New mass graves found as protesters demand justice for missing Mexican students
Thousands of Zapatista militias march during a demostration on Oct. 8, 2014 to demand justice in the case of the 43 students that went missing in Iguala. By Elizabeth Ruiz for Agence France-Presse.

Mexican authorities have found four new mass graves in the investigation into the disappearance of 43 students after suspects said some of the young men were buried there, officials said Thursday.

Four new suspects took investigators to the site of the 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, possibly dashing hopes among parents who refuse to believe their sons have died.

The four clandestine graves are "relatively" close to the location of another mass grave found last weekend in the southern state of Guerrero that contained 28 unidentified bodies, he said.

Authorities say 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 the students vanished after Iguala police officers working with the Guerreros Unidos gang shot at their buses in a night of violence on September 26 that left six people dead and 25 wound

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 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.

The mayor, his wife and public security director have apparently gone into hiding.

- Wife's cartel links -

Murillo Karam did not elaborate, but Mexican media, citing an intelligence services report, say Abarca's wife asked police to confront the students because she feared they would interrupt a speech she was giving that night.

The mayor then reportedly told the police chief to teach a lesson to the the students, who are from a teacher training college known as a bastion of protests.

The students say they were in Iguala to raise funds, though they had commandeered the buses to return home, a common practice among the radical aspiring teachers.

Guerrero chief prosecutor Inaky Blanco said authorities did not arrest Abarca before he disappeared last week because he has immunity as mayor, which has yet to be revoked.

Abarca requested a 30-day leave of absence before vanishing a few days after the attacks.

Blanco said Abarca faced state charges of negligence for preferring to stay at a party and go to bed instead of stopping the violence.

The mayor "left the victims at the mercy of public security members," Blanco said.

Four more municipal police officers have been arrested on homicide charges in the case, in addition to 22 who were detained last week.

Officials also arrested four alleged members of the Guerreros Unidos gang, which prosecutors say worked hand-in-hand with police during the assault.

Two Guerreros Unidos hitmen confessed to executing 17 of the students and dumping them in a mass grave.

- 'Act of barbarism' -

President Enrique Pena Nieto deployed federal forces to Iguala on Monday to take over security and disarm the local police. More than 100 officers were sent to a military base for retraining.

Pena Nieto vowed again on Thursday to punish those responsible for the "act of barbarism" and said he had instructed security officials to accelerate the investigation.

The Iguala case has embarrassed the mayor's leftist Democratic Revolution Party (PRD), which apologized for allowing him to run for office in 2012.

Governor Angel Aguirre, who is also a PRD member, has come under fire over the case but has repeatedly rejected calls by protesters to resign.

Hundreds of members of a citizen self-defense militia arrived in Iguala this week to carry out their own search for the students, interrogating people and digging for possible corpses.