Mexican federal police replaced local police and took control of 13 cities in southern Mexico amid allegations of connections to organized crime and a possible link to 43 missing students.

All 13 towns are within 125 miles of Iguala, where the students went missing about three weeks ago after a clash with police, according to a report from AP. Twelve of the towns are in Guerrero state and one is in Mexico state.

Monte Alejandro Rubido, Mexico's national security commissioner, said that in an investigation on the students' disappearance, authorities had found irregularities and "presumed links to organized crime" in the police forces of the 13 towns.

Rubido said that the replaced police officers are going to be interviewed and their performances will be reviewed. Their weapons also have been confiscated, BBC reported. Thirty-six police officers have been arrested in connection with the missing students.

Reports claim that officers in Iguala admitted to handing over the students to criminal cartel Guerreros Unidos. Both the mayor and police chief of Iguala are on the run.

Corruption in Mexico is fairly common, as drug cartels work with local government and security forces to make sure their criminal activity is allowed to continue. Mexican police are often poorly paid and undertrained, sometimes making them willing to work with organized crime to make more money.

On Friday, Mexican officials said they had arrested Sidronio Casarrubias Salgado, the alleged leader of Guerreros Unidos. He was detained Thursday on a highway leaving Mexico City, federal prosecutor Tomas Zeron said.

Attorney General Jesus Murillo Karam said he hopes the arrest of the cartel leader will help lead to more information on the missing students. The search for the students is ongoing and is being carried out by land, air and water with the help of relatives and the International Red Cross.

The disappearance of the students has outraged Mexicans and led to protesters marching recently in Mexico City, Acapulco and elsewhere in the country to demand their safe return.