A prison fire broke out on April 1 at La Toma prison in Amatlan de los Reyes, Veracruz state, Mexico.

According to the Washington Post, a group of incarcerated people started a fire in efforts to resist the transfer of four people to another jail, which happens to be a maximum-security federal prison. When local law enforcement (in support of the state police) went to the prison to begin the transfer process, they were greeted with an ambush by those in the cells.

During the incident, people escaped from their cells, BBC reports.

The four people who were supposed to be transferred have been identified as "highly dangerous" by the government for participating in criminal gang activities.

As a result of the revolt, seven incarcerated people were injured, including two that were particularly serious. Another 15 cops were hospitalized, including one with serious injuries. Additionally, six cops died via asphyxiation from the fire's smoke. A seventh person also died, but their identity—including whether they were incarcerated or an officer—is currently unknown. However, the person was not wearing a police uniform.

Prosecutors are investigating the incident.

Last week, a more deadly prison fire took the lives of nearly 70 people in Venezuela.