MEXICO CITY (AP) — The Mexican government announced rewards Monday of 1.5 million pesos ($111,000) for information on 43 students from a rural teachers’ college who have been missing since Sept. 26. 

The government ran full-page ads in Mexican newspapers with pictures of the 43 young men. The government also offered 1.5 million pesos for information on those who had abducted or killed the students. 

The government says it still does not know what happened to the students of the radical teachers’ college, after they were rounded up by local police and allegedly handed over to gunmen from a drug cartel. 

About 50 people have been arrested or detained in the case, including police officers and suspected members of the Guerreros Unidos cartel. 

Analyses of remains found in mass graves have so far not matched the students.

As part of the effort to search for the students — which now includes, air, ground water-borne patrols — and bring order to the violent region of southern Mexico, federal police took control of 13 municipalities in southern Mexico where local police are suspected of links to organized crime. 

The municipalities are all within a roughly 125-mile (200-kilometer) radius of Iguala, in the southern state of Guerrero, the town where the students from a rural teachers’ college disappeared more than three weeks ago after a confrontation with police. Twelve of the municipalities are in Guerrero state and one is in Mexico state. Among them are the tourist destinations of Taxco and Ixtapan de la Sal.

National Security Commissioner Monte Alejandro Rubido said Sunday night that authorities investigating the disappearance of the students found “irregularities” and “presumed links to organized crime” in the 13 municipal police forces.

Federal police have assumed control of public security in the municipalities, the police chiefs have been sent to a special center for “certification” and their guns are being tested, he said. 

Federal forces had already disarmed local police in Iguala and Cocula, and arrested a total of 36 police officers. Both the mayor and police chief of Iguala are fugitives and accused of links to the local drug cartel, Guerreros Unidos, believed to have worked with police in disappearing the students. 

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

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

Attorney General Jesus Murillo Karam had said he hoped the arrest would bring new leads in the case. 

Rubido said Sunday night that the search for the 43 students is being carried out with the help of relatives and the International Red Cross.