Mexican prosecutors will take new testimony from federal security officials to determine what part they played during the disappearance of 43 students training to be teachers last year, which battered the government's image at home and abroad.
Families of the victims and an independent experts have pushed to clarify what the army and federal police did on the night of Sept. 26, 2014, when the students clashed with local police in the southwestern city of Iguala before disappearing.
"Everything needed to settle the case will be investigated, everything," said Eber Betanzos, deputy attorney general for human rights, who will head a new inquiry into the case.
The new probe would include the questioning of federal forces, both those who had already been interrogated and those who had not, he said in an interview with Reuters this week.
The disappearance of the 43 students created a political storm for President Enrique Peña Nieto over his government's shortcomings in the fight against corruption and impunity.
Attempting to clear up the case, then-attorney general Jesús Murillo said in November the students were abducted by corrupt local police, handed over to a drug gang, and incinerated in a rubbish dump before their ashes were thrown into a river.
But a panel of international experts last month rejected the notion that all the students' bodies were burned at the dump, saying the investigation was full of holes. So far only the remains of one of the students has been definitively identified.
The team of respected investigators raised suspicions of forced confessions and possible collusion by security forces, including the army, which has a barracks at Iguala.
Bowing to international and domestic pressure, the government last week said it would mount a new search for the 43, working with the international experts and using advanced technology such as drones and satellites.
That came after the head of the army dismissed the idea of allowing the international experts to directly question troops and rejected suggestions of their involvement - despite recent abuses tied to the military.
The new investigation will also look into the possible use of torture during the government's prior inquiry, and could extend to the whole country if necessary, Betanzos said.