The Mexican attorney general's office hit back Monday at mounting criticism of its conclusion that 43 missing students were slaughtered, after foreign experts charged that the probe was marred by mistakes.
An Argentine-led team of forensic experts said that while they could not exclude the possibility that the students were incinerated in a landfill by a drug gang, there was "no scientific evidence" to say that for sure.
But the prosecutor's office issued a statement rejecting the "poorly defended arguments" of the Argentine Forensic Anthropology Team, which was hired by parents of the 43 young men to participate in the probe.
"It is unacceptable that -- in the face of a body of evidence, expert (investigations), confessions, statements and investigative inspections -- there are attempts to sow doubts that around 40 people were executed and incinerated in that location," the statement said.
Attorney General Jesus Murillo Karam declared on January 27 that the "historical truth" was that the aspiring teachers were murdered in the southern state of Guerrero in September after corrupt police handed them over to the gang.
Only one of the students was identified among the charred remains.
Human rights groups have criticized Murillo Karam's conclusions, saying the investigation relied too much on witnesses in a country where authorities often get coerced confessions.
The case has sparked angry protests, engulfing President Enrique Pena Nieto in the biggest crisis of his administration.
- Amnesty 'whitewash' warning -
For parents of the victims, who have never believed the authorities, the Argentine team's report "makes it clear that the 'historical truth' has fallen to pieces," said Felipe de la Cruz, spokesman for the parents.
The authorities "believe in the statements of assassins more than scientific evidence," he told a news conference.
Amnesty International, which has urged Mexico to continue the investigation, said the Argentine team's report has cast "very real doubts" about Murillo Karam's conclusions.
"The attorney general's eagerness to close this case based on what has now been revealed to be a biased position that is unsupported by evidence begins to look worryingly like a whitewash," said Erika Guevara Rosas, Amnesty's Americas director.
The Argentine experts noted on Saturday that several fires had been set at the landfill since 2010, meaning physical evidence collected at the site could belong to previous unrelated events.
- Prosecutors fire back -
But prosecutors responded that all evidence links the site of the ashes to the day the students went missing, and that any "opinion to the contrary is hypothetical and far from reality."
Among other complaints, the Argentines said they were not present in late October when divers found a bag filled with charred remains that was dumped in a river at the bottom of the landfill in Cocula.
The attorney general's office said the Argentine team had been invited to the site the night before, but decided to focus on the garbage dump instead.
Authorities admitted that they had made mistakes in 20 of the 134 genetic profiles provided by parents of the missing but that it was corrected within 24 hours.
The genetic profiles were sent to a world-renowned forensic lab at Austria's University of Innsbruck, which was only able to identify one of the students among 17 sets of remains sent by Mexico.
After the remains were recovered, the dump site was left unguarded between November 7 and 27, suggesting that any evidence found during that period could be dismissed.
The Argentines said investigators returned to the site on November 15 and collected 42 bullet casings without them present.
But prosecutors said they had agreed with the Argentine team that the location no longer needed to "remain preserved," and that it was not invited back in November because ballistics are not its expertise.