Prosecutors said that gunmen dressed in armor attacked the El Paso state prison early Sunday. They killed 10 guards and four prisoners.

According to a statement from the Chihuahua State Prosecutor’s Office, several armed vehicles arrived at Ciudad Juarez’s state prison at 7:15 a.m. and opened fire on guards.

Later Sunday, Mexican soldiers and the state police took control of the prison. According to the state prosecutor’s office, its personnel are investigating.

A riot broke out in August at the state prison, which spread to Juarez’s streets, leaving nearly a dozen dead.

Two inmates were shot to death inside the prison. Then, gang members allegedly began shooting up the town. Four employees of a radio station were also killed while they were promoting a restaurant.

Violence is a common occurrence in Mexican prisons, even in those where authorities have only a minimal control. Inmates from rival gangs are often involved in violent clashes that can lead to violence. These gangs in Mexico, such as Juarez, serve as proxy for drug cartels.

According to a statement from the state prosecutor’s office, four men were captured by police officers in the municipality shortly before the attack on Sunday’s prison. Two alleged gunmen were later killed by police while traveling in an SUV.