Mexico's government said on Friday evidence suggests that 43 missing trainee teachers were murdered and their charred remains tipped in a rubbish dump and a river in southwest Mexico, based on the confessions of three detained gang members.
Attorney General Jesus Murillo said the detainees, caught a week ago, admitted setting fire to a group of bodies in a dump near Iguala in the state of Guerrero, where the students went missing on Sept. 26 after clashing with police.
Then, the perpetrators set about removing all the evidence, Murillo told a news conference, showing taped confessions of the detained, photographs of where remains were found and video re-enactments of how the bodies were moved.
"They didn't just burn the bodies with their clothes, they also burned the clothes of those who participated," Murillo said. "They tried to erase every possible trace."
The government says police working with a local drug gang abducted the students after the clashes. The kidnapping triggered mass protests in much of the country and seriously undermined President Enrique Pena Nieto's claims that Mexico has become safer on his watch.
The disappearances have been the toughest challenge yet to face Pena Nieto, who took office two years ago vowing to restore order in Mexico, where about 100,000 people have died in violence linked to organized crime since 2007.
A grim-faced Pena Nieto said the findings had "shocked and offended" Mexico and pledged to round up everyone involved.
"The investigations will be carried out to the full, all those responsible will be punished under the law," he said.
Dozens of police are among 74 people held in the case.
The confessions of the gang members pointed to the murder "of a large number of people," Murillo said, showing a video of one suspect saying the victims had said they were students.
Identifying the remains, which were ground up after burning, was so difficult that it was impossible to say when final results would come in, Murillo said. But there was much evidence "that could indicate it is (the students)," he added.
Teeth of victims found at the scene were so badly burned that they virtually turned to dust upon contact, Murillo said, adding that the remains would be sent to the University of Innsbruck in Austria for final DNA identification.
The government would continue to view the students as missing until their identities are confirmed, he added.
This week, Mexican police captured the former mayor of Iguala and his wife, who the government suspects of being the probable masterminds of the abductions.
Testimony from investigators suggested that the students, from an all-male leftist college, had clashed with the mayor in the past and that the city police had handed them over to local gangsters who killed them.
The case has dented Pena Nieto's popularity and derailed his efforts to turn public attention toward a string of reforms he passed in the first part of his government, which he hopes will spur stronger growth in Mexico's misfiring economy.
