Updated

Thousands of protesters marched along Acapulco's famed coastal boulevard Friday demanding the safe return of 43 missing students from a rural teachers college, and federal officials announced a key arrest that could produce new leads.

Mexican officials announced the arrest of Sidronio Casarrubias Salgado, the purported leader of the Guerreros Unidos drug gang suspected of acting with local police in taking away the students. He was detained Thursday on a highway leaving Mexico City, federal prosecutor Tomás Zerón said.

Attorney General Jesús Murillo Karam said he hoped the arrest will bring new leads in the case.

The government is combing the hills of southern Guerrero state with horseback patrols and has divers looking in lakes and reservoirs behind dams, but has not found the youths missing since a confrontation with police Sept. 26 in the city of Iguala. Officers are suspected of turning the students over to the gang.

Authorities have arrested 36 police officers along with 17 alleged members of the gang.

Casarrubias didn't order the disappearances, but he knew about them and didn't object, Murillo Karam said. The suspect told authorities he spent a total of $45,000 a month in payoffs to police in Iguala and the neighboring town of Cocula, the attorney general said.

Iguala Mayor José Luís Abarca and his wife, Maria de los Angeles Piñeda, are being sought for their presumed involvement in the disappearances, Murillo Karam said.

Activists in Guerrero hold out hopes that the missing youths are still alive and have pledged to blockade city halls across the state until they are found.

A caravan of more than 20 buses from the teachers college attended by the missing students joined other protesters from the state's teachers union in downtown Acapulco on Friday for the emotional but peaceful demonstration calling for authorities to resolve the case.

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