MEXICO CITY (AP) — A study published by a children’s rights group in Mexico Monday suggests there has been a disturbing pattern at as many as 18 schools and childcare centers where multiple adult employees allegedly collaborated among themselves and used eerily similar tactics and practices to sexually abuse pupils between the ages of three and seven.

In one case uncovered in 2018, 11 adults at one pre-school allegedly abused 49 children aged between 3 and 5, by inserting water-filled syringes into their bodily orifices, a practice found over and over in other cases.

The “11 offenders are accused of committing the abuse in a coordinated fashion,” according to the report by the civic group Center for The Defense of Children’s Rights. Children were forced to watch adults performing sexual acts or touch or abuse other kids. In many cases, the similar use of disguises or specific staging of the abuse suggested a broader pattern.

“The cases identified are notably different from the unfortunately numerous cases of child sexual abuse committed by individual teachers against one or more students,” the report states. “These cases demonstrate patterns of criminal behavior characterized by organized aggressions committed by multiple adults perpetrated in mass scale within the premises of a given school.”

“Evidently this situation raises questions as to how these perpetrators came to work in the same school? How were they assigned to this post and by whom? How did their coordinated action come to be? Did they arrive to this post knowing each other or did their coordination arise once working in the school?” the report asks.

“We have identified patterns of criminal behavior that raise the possibility that numerous primary and pre-school facilities have been coopted and used to commit on-line child sexual abuse,” the report states.

Asked about the report, President Andrés Manuel López Obrador pledged Monday to provide an accounting of how the government is combating such cases.

“A lot of work is being done, all these reprehensible, appalling acts that involve the abuse of children are being combated, it is an ongoing activity,” López Obrador saying he would instruct the appropriate authorities to report on “how children, the most vulnerable segment of the population are being protected from these attacks.”

Some of the cases in which the Center’s lawyers have participated have resulted in convictions of abusers. For example, in one 2011 case, six school employees were convicted and received lengthy prison sentences.

But the lawyers were struck both by the brazenness of the abusers, and a pattern that seemed to be repeated at other schools. For example, the report states that in the 2011 case, “those found guilty include the school’s principal, four teachers, and the school janitor. The patterns in the abuse and extreme violence are repeated in multiple schools. The abuse takes place within the school and perpetrators do not seem to hide when committing the repeated abusive behavior.”

So the legal team reviewed 37 cases found “to possibly match the criminal patterns we identified. Of these cases we were only able to attain greater detail as to the narratives of the children in 18 schools that confirmed similar patterns.”

But the report says that police investigations are poorly coordinated with prosecutors, and tend to prosecute abusers as individuals, without looking at whether even more accomplices were involved.

“Organizational links between similar cases are impossible to detect if each school is investigated in an isolated manner,” the report says. “Fragmentation guarantees criminal organizations that it is technically impossible to detect any participation other than the material offenders in any given case.”

Moreover, many of the victims report there were cameras present during the abuse, raising the possibility the abuse was being filmed or photographed for later distribution. “We considered that a possible hypothesis of the production of child pornography should be investigated,” according to the report.