Following a five-hour meeting with the president, relatives of the students abducted by police in late September in the southwestern city of Iguala dismissed his efforts to find the missing and said their patience was running out.
The disappearances have become arguably the sternest challenge yet to face Pena Nieto, who took office two years ago vowing to restore order in Mexico, where close to 100,000 people have died in violence linked to organized crime since 2007.
Initial testimony from investigators suggested that the students, who belong to an all-male leftist college, had a history of conflict with the Iguala mayor and that the city police had handed them over to local gangsters who killed them.
But their fate remains unclear.
“We’re not going to believe the president’s words and the pledges he made until the 43 students are presented to us alive,” one of the fathers, Felipe de la Cruz, told a news conference late on Wednesday after meeting Pena Nieto.
“With all the power the state has, they can’t find our boys. We’re not going to believe in this deceit,” he added.
Both the mayor of Iguala and his wife have gone on the run. Dozens of arrests have been made and at least 38 bodies have been dug up in the hills around the city, but so far none have been identified as those of the missing students.
Minutes before the relatives lined up in front of cameras, many of them clutching placards emblazoned with faces of the students, Pena Nieto made a televised address in which he pledged to redouble efforts to find the missing youths.
“There will not be the slightest room for impunity,” the president said. “We must apply the law whoever it affects.”
Security forces have combed the area around Iguala in search of the students, whose disappearance has sparked massive protest marches in Mexico. The row has also prompted the governor of the surrounding state of Guerrero to step down.
Another of the fathers, Epifanio Alvarez, said the talks on Wednesday had left the families feeling desperate.
“This meeting is just like the others we’ve had with the attorney general and the interior minister: it’s the same as always. There really is no answer from anyone,” he said.
Emiliano Navarrete, also one of the fathers, was more blunt.
“What fills me with rage are the actions of the government, because it’s supposed to help us,” he said.
The problem, said de la Cruz, was the government’s failure to stamp out political corruption.
“There’s impunity in the government, not just in Guerrero; there’s impunity in municipal, state and federal governments,” he said. “Because we know that many of them are involved with organized crime too.”
(Writing by Dave Graham; Editing by Crispian Balmer)