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, citing the confessions of three detained gang members.

Attorney General Jesus Murillo said the detainees, caught a week ago, admitted setting fire to members of the group in a rubbish dump near Iguala in the state of Guerrero, where the students went missing on Sept. 26 after clashing with police.

Police working with a local drug gang abducted the students after the clashes, triggering mass protests and seriously undermining President Enrique Pena Nieto's claims that Mexico has become safer on his watch.

Dozens of police are also among more than 70 people held in connection with the case.

"There are many indications ... that could indicate it is them," Murillo told a news conference, after showing taped confessions of the detained, photographs of the location where remains were found and video re-enactments of how the bodies were moved.

"The confessions we have gathered ... very sadly point to the murder of a large number of people," he added.

Teeth of victims found at the scene were so badly burned that they virtually disintegrate into dust upon being touched, Murillo said.

Mexico's government is still waiting for DNA confirmation from Argentine forensic anthropologists to confirm the identity of those killed.

Murillo said the government would continue to view the students as missing until remains are confirmed to match their identities.

This week, Mexican police captured a fugitive former mayor and his wife who the government suspects of being the probable masterminds behind the abduction of the students.

The case has sparked mass street protests, civil unrest in Guerrero and anger over the government's failure to crack down on links between politicians and organized crime.

It has also derailed Pena Nieto's efforts to turn public attention to his efforts to revive Mexico's misfiring economy and attract investment after years of gang violence that has claimed about 100,000 lives since the start of 2007.