MEXICO CITY — Federal police have taken control of 13 municipalities in southern Mexico where local police are suspected of links to organized crime and possibly to the case of 43 missing students, a top official said.

The municipalities are all within a roughly 125-mile radius of Iguala, 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 making the students disappear.

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 by land, air and water with the help of relatives and the International Red Cross.