U.S. authorities inadvertently helped to cause the deaths of thousands of people in Allende, Mexico in 2011 after information they gathered was leaked to the Zetas cartel’s leaders, according to journalist Ginger Thompson.

In 2011, Drug Enforcement Agency officials informed Mexican authorities about a secret operation involving surveillance on multiple cellphones that belongs to leaders of the Zetas cartel, which had recently "swept through" Allende and the nearby towns, according to Thompson. This information was eventually leaked to those leaders, who subsequently ordered the killings of anyone who could have been an informant, along with their families and anyone else who could have been close to them.

The incident and the events leading up it were covered by Thompson in the 2017 report for ProPublica titled, "How the U.S. Triggered a Massacre in Mexico," which Netflix recently adapted as a miniseries titled "Somos."

"I started this story because I was aware that there are many tragedies like the one in Allende, but this one in particular could show a direct link to the US," Thompson told Business Insider on Friday.

"I think the story of Allende has sort of been heard in Washington. There are investigations happening as a result of that story. The Mexican government has heard and talked about what happened in Allende as a result of 'Somos,' but we'd be kidding ourselves if we think this will solve the problem," she said. 

Former chief of international operations for the DEA Mike Vigil, who spent nearly 20 years working in Mexico, told Insider that they could have avoided the massacre, which resulted in the deaths of thousands.

"When you work with or in Mexico you have to be very careful with the information you are sharing. You could end up with a horrific situation like what happened in Allende," he said.

"I think the DEA made a huge mistake by sharing information, but they've learned from that mistake. Now the ones that have to learn from this are the Mexican government," Vigil added.

He went on to say that now that Mexico has reformed its National Security Law, authorities from the U.S. could find themselves connected to another massacre similar to the incident in Allende.

"This new law is requiring all foreign agents to report any interaction with Mexico. This means that all of the sensitive information is going to be shared with unknown Mexican officials and could jeopardize not only operations but many lives," Vigil said.

One state police intelligence agent, who spoke to Insider on the condition of anonymity, noted that "after learning what happened in Allende and watching the series on Netflix the feeling I have is that nothing has changed. Organized crime keeps on top of the game and collud[ing] with most Mexican authorities."

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