The case of 43 Mexican students missing since an attack by gang-linked police took another grim turn Thursday with the discovery of new mass graves where suspects said some were buried.
Four new suspects took investigators to the site of the four pits, 200 kilometers (125 miles) south of Mexico City, but the number of bodies remains unknown, said Attorney General Jesus Murillo Karam.
"They say there are remains of students," Murillo Karam said, adding that some of the bodies appeared burned.
The discovery has put another dent on hopes of finding the students alive almost two weeks after they were pursued by Iguala police officers accused of working in tandem with the Guerreros Unidos gang.
The pits are "relatively" close to the location of another mass grave found last weekend in the southern state of Guerrero that contained 28 unidentified bodies, the attorney general said.
Two hitmen confessed to executing 17 of the students and dumping them in the mass grave found last Saturday.
Authorities have said it will take at least two weeks to identify the bodies through DNA analysis.
The case has outraged Mexicans, who held protests across the country Wednesday to demand the return of the students, in a nation that has lost tens of thousands of people to drug violence since 2006.
Authorities say crooked officers shot at buses the students had seized to return home on September 26, sparking a night of violence that left six people dead, 25 wounded and 43 missing.
Surveillance cameras showed several students being taken away in patrol cars.
Murillo Karam said there are several lines of investigation into the motive but that the city's mayor, Jose Luis Abarca, his wife and the public security director are wanted for questioning.
The trio have apparently gone into hiding.
The mayor's wife, Maria de los Angeles Pineda Villa, is the sister of two late members of the Beltran Leyva drug cartel, which founded the Guerreros Unidos.