Per 
Special Containment Procedures: SCP-XXXX is contained on site in Lake Alchichica in The Oriental Basin, Mexico. Public access to containment site is to be prohibited on the grounds of the protection of a critically endangered species. A 10 meter concrete wall equipped with 10 high powered speakers and accompanying floodlights surrounds the containment site.
SCP-XXXX-A and B are to be fed one tenth their presently estimated body masses in raw meat of any type three times per week (assuming each individual specimen of SCP-XXXX weighs 125 grams). SCP-XXXX-C's diet it to be determined weekly by the present chief biologist of Containment Area XXXX-C. SCP-XXXX is to be actively monitored and any notable change in behavior is to be reported to the current site director.
An SCP-XXXX population increase or decrease of at least 50% at any containment site is considered unusual behavior and requires an examination of the surrounding ecology and the health of SCP-XXXX individuals. If any amount of SCP-XXXX's population is determined to be unwell the infected population of SCP-XXXX is to be separated and monitored. If the illness proves to maintain through SCP-XXXX's reproduction process the infected population is to be euthanized as to maintain the general health of SCP-XXXX's population.
In the event of an attempted mass containment breach by SCP-XXXX the containment area's high powered speakers and floodlights are to be manually activated in order to herd masses of SCP-XXXX back into its containment. Physically approaching SCP-XXXX during an attempted breach should be done only if absolutely necessary. If any number of SCP-XXXX breach containment all bodies of fresh water in a 0.5 kilometer radius are to be monitored for SCP-XXXX over the following 48 hours.
Addendum-XXXX-A: As of Incident-XXXX-1 Lake Aljojuca is now designated as Containment area XXXX-B and serves as a secondary containment site for SCP-XXXX. Furthermore the removal of a living specimen of SCP-XXXX from either containment site is strictly prohibited, any and all study of a living instance of SCP-XXXX is to be done on site.
Addendum-XXXX-B: As of Incident-XXXX-2 the ████████ Lake is now designated as Containment Area XXXX-C. An avian-proof metal net is to be installed over all containment sites. Due to the volatile behavior of SCP-XXXX-C Containment Area XXXX-C is considered the highest priority of containment. Containment area XXXX-C will be the base of operations for on site security and environmental investigations in the event of a containment breach.
Foundation agents stationed in the Oriental Basin area are to monitor wildlife activity in the region to ensure further populations of SCP-XXXX are contained as quickly as possible. At time of recording there is an estimated 5000 instances of SCP-XXXX composing SCP-XXXX-A, 2500 instances composing SCP-XXXX-B, and ████ instances composing SCP-XXXX-C
An individual instance of SCP-XXXX
Description: SCP-XXXX is a subspecies of Ambystoma mexicanum (Axolotl) that is capable of regenerating lost body tissue at rates far exceeding that of typical members of the species. Being able to perfectly regenerate body mass at a rate of up to 150 grams per minute. When under severe stress SCP-XXXX has been known to increase its rate of regeneration to up to 400 grams per minute, however tissue regenerated at any rate faster than the typical 150 grams per minute is at risk of being subject to mutations of varying severity. These mutations are at the genetic level and will be passed down to any and all offspring of the mutated individual.
SCP-XXXX demonstrates an unlimited degree of bodily autotomy and can voluntarily shed any body part at will with no apparent physical suffering or lasting scarring. Any body part shed or forcibly removed from SCP-XXXX that exceeds 5% of its body mass will immediately begin growing a new body at a rate identical to the main body. This process results in a clone of the parent SCP-XXXX specimen. This is the only means by which SCP-XXXX is known to reproduce.
Containment Area XXXX-A prior to containment measures being established
All instances of SCP-XXXX work in perfect coordination with one another. When not in danger SCP-XXXX will school in such a way that as a unit they behave as a single gargantuan instance of Ambystoma mexicanum. Despite their coordination as a larger unit SCP-XXXX has proven to posses very low intelligence, as demonstrated by SCP-XXXX's frequent difficulty recognizing food and inability to comprehend non-threatening stimuli. The three SCP-XXXX schools in containment are designated as SCP-XXXX-A, SCP-XXXX-B, and SCP-XXXX-C. SCP-XXXX individuals that are part of schools have been seen rapidly reproducing in order to "regenerate" separated parts of the school. When under assault an SCP-XXXX school will separate into individual units and scatter to avoid capture. However nonphysical deterrence measures such as loud sounds and bright lights will not trigger this scattering activity.
SCP-XXXX-A and SCP-XXXX-B are, despite their size difference, functionally identical in appearance and behavior. Both acting like a large member of Ambystoma mexicanum. Unlike other schools SCP-XXXX-C is highly volatile in behavior. This unstable behavior usually manifests as individual components of SCP-XXXX-C fighting amongst each other and frequent attempts to breach containment. The fighting between individuals as well as the poor overall health of SCP-XXXX individuals within SCP-XXXX-C make these breach attempts easy to quell. However SCP-XXXX-C's high rate of growth compared to SCP-XXXX-A and B still requires the Foundation give special care to containing SCP-XXXX-C.
Discovery: SCP-XXXX was brought to Foundation's attention after multiple civilian reports of a lake monster residing in Lake Alchichica. Foundation Agent Betancourt was sent to investigate and quickly discovered SCP-XXXX-A, Agent Betancourt however assumed the school to be a singular entity. Mobile Task Force Lambda-12 ("Pest Control") was sent in to retrieve SCP-XXXX. It was then discovered SCP-XXXX's true nature as a swarm of identical individuals. This proved to make capture of SCP-XXXX difficult due to its "break and scatter" behavior. After 4 hours of trying to manually capture SCP-XXXX individually or in small clusters only to make no progress on lowering SCP-XXXX's population it was decided to contain SCP-XXXX on site in order to prevent further multiplication.
Incident-XXXX-1: On 3/14/2002 10 live specimens of SCP-XXXX were taken offsite to be examined at a freshwater wildlife laboratory in Mexico City. before the vehicle transporting the SCP-XXXX specimens was able to leave The Oriental Basin SCP-XXXX had produced enough duplicates to breach not only its transport tank but the wall of the vehicle itself. The newly formed school of SCP-XXXX, the school, newly designated as SCP-XXXX-B, then proceeded to wander the countryside for several hours before MTF-Lambda-12 was able to lure the school into the nearby Lake Aljojuca. During that time SCP-XXXX had duplicated an estimated 2500 individuals. Lake Aljojuca was declared a secondary containment site and containment procedures were updated accordingly.
Incident-XXXX-2: On 10/22/2004 an unidentified bird of prey captured a single instance of SCP-XXXX. The standard issue firearms used by site security proved unable to terminate the predator before it escaped the containment walls and the instance of SCP-XXXX it had captured was presumed dead. However during the required subsequent sweep of the area surrounding Containment Area XXXX-A over ████ instances of SCP-XXXX were found both dead and alive outside the containment zone. These individuals found were heavily mutated in ways including an abnormal number of various organs and limbs, including those unique to species' other than Ambystoma mexicanum. While these instances of SCP-XXXX exhibited similar schooling to that of SCP-XXXX-A and SCP-XXXX-B the unit's behavior was highly erratic. During the attempts to contain the school, now designated as SCP-XXXX-C, four members of MTF-Lambda-12 were injured due to SCP-XXXX-C's sheer size as well as specific dangerous mutations by individuals, one instance being serrated claw-like bone protrusions able to compromise MTF-Lambda-12's chemical hazard wear. SCP-XXXX-C was contained in Containment Area XXXX-C and containment procedures were updated in order to accommodate for the differences between SCP-XXXX-C and the other SCP-XXXX schools.
Following Incindent-XXXX-2 a foundation committee assembled to determine if SCP-XXXX should be upgraded to Keter classification. Despite a vocal minority citing the randomness of mutations caused by SCP-XXXX-C making containment unreliable as well as the unknown uncontained population of SCP-XXXX the committee voted 7-2 to retain SCP-XXXX's Euclid status. Below are statements from representatives of concurring and dissenting members of the committee.
Commander Kevin Maroto of MTF Lambda-12: Listen, it's not like my guys haven't dealt with worse stuff in the past. Honestly the fact that you can even see these little weirdos without a microscope and they don't turn into ████ing cars that try and mow us down1 means these guys are tamer than most of what my boys see on the day-to-day. So what if they know their playbooks? So do we. Working as a team ain't special if you're scared of some blinky lights. The MTF members that got hurt will be fine, the lizards can't do any real damage this far out in the middle of nowhere.
Dr. Allison Boyd of the Foundation Herpetology Department: Just because we've been able to recapture SCP-XXXX the two times it's breached containment doesn't mean it won't be able to break out again and cause even more problems. What if it gets out again and we find out it can reproduce even faster than we thought? What if there's some massive underground lake full of the things just waiting to break through to the surface? The point of the object classification is to stop preventable containment breaches. Not shrug our shoulders when a breach does happen and say "hindsight is twenty-twenty nothing we could do." Incident-XXXX-2 should have been the wake up call to start taking things seriously and stop letting Commander Maroto treat this like some big game of sharks and minnows, because I'm worried there might be a time where Pest Control won't be the sharks anymore.
Addendum-XXXX-C: On 1/6/2005 an examination of SCP-XXXX's cellular structure was conducted in an attempt to determine the source of SCP-XXXX's supernatural cellular regeneration rate. Upon examination by Dr. Boyd it was discovered that in place of typical animal cells SCP-XXXX's entire body is made up of millions of microscopic creatures that are superficially identical to SCP-XXXX. Shortly after this discovery Dr. Boyd requested reassignment and appointed Dr. Manuel Rodríguez to supervise research into SCP-XXXX. Research is now ongoing into the nature of SCP-XXXX's cells although tests thus far have been inconclusive.
Sources
SCP-XXXX: Scarlet H S Jensen from https://www.flickr.com/photos/charlotteshj/3755674856/
Lake Alchichica: AnyPReyes from https://commons.wikimedia.org/wiki/File:Laguna_de_Alchichica_Puebla.jpg
