Federal police in Mexico have taken over 12 towns in the state of Guerrero after authorities learned of possible connections between local law enforcement and organized crime.

National Security Commissioner Monte Alejandro Rubido said at a Sunday press conference that the links were uncovered during an investigation into the disappearance of 43 students in the town of Iguala last month, Bloomberg News reports.

Earlier this month, Guerrero prosecutor Iñaky Blanco said that the gang Guerreros Unidos had worked with area police and killed 17 of the missing students. Mass graves were discovered in the area in early October, but remains in the first grave didn’t belong to any of the missing students.

More than four dozen people, including members of Iguala police and various alleged gang members, have been detained on suspicion of kidnapping the missing students.

[Bloomberg News]

Write to Nolan Feeney at nolan.feeney@time.com.