Story highlights Officials tell families of missing students about the arrest after a day of protests

Families reject official accounts and demand proof

Cesar Nava Gonzalez had been on the run since the students disappeared, authorities say

Nava allegedly helped round up the 43 students and hand them over to a drug gang

A top local police official in Mexico was arrested in connection with the disappearance of 43 college students, authorities said.

Investigators apprehended Cesar Nava Gonzalez, the former deputy director of the Cocula police department who had been on the run since the September disappearance of the students, the federal prosecutor's office said.

Nava allegedly was called to the neighboring town of Iguala, in Guerrero state, and allegedly helped round up the 43 students and hand them over to a drug gang to be massacred, authorities said.

The police chief of Iguala still has not been apprehended, authorities said.

The Prosecutor General's office informed families of the missing students about Nava's arrest on Friday, a day after massive protests to denounce political corruption and impunity in the case.

The 43 missing students went missing September 26 after they and others traveled in buses about 77 miles from their rural teachers college in Tixtla to Iguala. They went there to protest a speech by the mayor's wife.

But a violent clash with police left six people dead, including three other students.

Photos: Protests over missing Mexican students Photos: Protests over missing Mexican students People march Monday, January 26, during a protest in Mexico City for the 43 college students who went missing four months ago in the Mexican state of Guerrero. A day later, Mexican Attorney General Jesus Murillo Karam said there is "legal certainty" that the students "were abducted, killed, burned and thrown into the San Juan River, in that order." At least 99 suspects have been detained so far. Hide Caption 1 of 22 Photos: Protests over missing Mexican students People march January 26 in Mexico City. The students attended Escuela Normal Rural de Ayotzinapa, a rural teachers college known for its political activism. Hide Caption 2 of 22 Photos: Protests over missing Mexican students Hundreds of police officers in riot gear block a street during several marches in Mexico City on January 26. Hide Caption 3 of 22 Photos: Protests over missing Mexican students A masked protester waves a Mexican national flag during protests in Mexico City on January 26. Hide Caption 4 of 22 Photos: Protests over missing Mexican students A man smashes the window of a traffic patrol vehicle during a protest in Chilpancingo, Mexico, on Thursday, January 15. Hide Caption 5 of 22 Photos: Protests over missing Mexican students Military police spray tear gas during a protest in Iguala, Mexico, on Monday, January 12. Hide Caption 6 of 22 Photos: Protests over missing Mexican students A man burns an effigy of Mexican President Enrique Pena Nieto during a protest in Mexico City on Wednesday, December 31. Hide Caption 7 of 22 Photos: Protests over missing Mexican students Hundreds of residents of Ayutla, Mexico, and parents of the missing students participate in a protest on Wednesday, December 17. Hide Caption 8 of 22 Photos: Protests over missing Mexican students People gather during the protest in Ayutla on December 17. Hide Caption 9 of 22 Photos: Protests over missing Mexican students Riot police confront protesters near the airport in Mexico City on Thursday, November 20. Hide Caption 10 of 22 Photos: Protests over missing Mexican students A protester holds up a poster parodying Pena Nieto during a rally in Mexico City on November 20. Hide Caption 11 of 22 Photos: Protests over missing Mexican students A woman holds flowers and a candle during the November 20 demonstration. Hide Caption 12 of 22 Photos: Protests over missing Mexican students Police guard the National Palace in Mexico City as protesters and police clash on November 20. Hide Caption 13 of 22 Photos: Protests over missing Mexican students Demonstrators clash with riot police on November 20. Hide Caption 14 of 22 Photos: Protests over missing Mexican students An injured protester gets first aid on November 20. Hide Caption 15 of 22 Photos: Protests over missing Mexican students People on the base of a monument watch and cheer on marchers in Mexico City on November 20. Hide Caption 16 of 22 Photos: Protests over missing Mexican students A protester cries as police attempt to detain her and human rights observers try to reach her during a march near the Mexico City airport on November 20. Hide Caption 17 of 22 Photos: Protests over missing Mexican students A protester lights a firework as demonstrators march on November 20. Hide Caption 18 of 22 Photos: Protests over missing Mexican students Riot police surround protesters who had thrown Molotov cocktails and destroyed vehicles in Mexico City on November 20. Hide Caption 19 of 22 Photos: Protests over missing Mexican students A police officer falls after a protester threw a Molotov cocktail on November 20. Hide Caption 20 of 22 Photos: Protests over missing Mexican students Protesters gather November 20 at the Angel of Independence monument in Mexico City. Hide Caption 21 of 22 Photos: Protests over missing Mexican students Students place school desks with photos of the missing students in a plaza at Mexico's National Autonomous University on November 20. Hide Caption 22 of 22

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Authorities believe the 43 students were captured by Iguala police and turned over to a gang in cartel territory and then executed in Cocula, 14 miles away.

The gang burned the bodies and dumped them in a river, but their corpses have yet to be found, authorities say.

A mayor arrested, too

So far, authorities have also charged Iguala Mayor Jose Luis Abarca as the "probable mastermind" in the 43 students' disappearance, and he has been charged with six counts of aggravated homicide and one count of attempted homicide, authorities said.

In all, at least 75 people have been arrested in connection with the disappearances and the deaths, and the governor of Guerrero has taken a leave of absence amid scorching criticism that he responded too slowly to what's been called one of the most serious human rights abuses in recent Latin American history.

Federal authorities say they heard confessions from drug traffickers indicating that the college students were rounded up on the orders of the Iguala mayor and then delivered to the drug gang to be murdered.

Families don't accept the official version and demand proof of what happened.

Mexicans have rallied to support the families, and on Thursday, tens of thousands of people converged on Mexico City to vent their anger and frustration in a protest that ended in violent clashes with police.

The 43 missing students attended la Escuela Normal Rural de Ayotzinapa, a small college devoted to training students to become teachers in Mexico's impoverished countryside.

Leftist school

The rural teachers' colleges, sometimes labeled normal schools, are called "devil schools" by critics, according to Luis Hernandez Navarro, editor of La Jornada, one of Mexico's major newspapers.

"These are schools that are poor, and for the poor, to teach the poor," Hernandez told CNN.

"These schools are the gateway to move socially for the poor, rural students," Hernandez added, "and they are one of the few escape routes that farmers have for their children to become teachers and prosper."

The school has been in the government's cross hairs, and business groups have requested they be closed, he added.