Argentine-led forensic experts strongly criticized Mexico's investigation into the presumed massacre of 43 missing students on Saturday, insisting the probe must remain open as they listed a series of mishaps.
The Argentine Forensic Anthropology Team, with experts from 30 countries including the United States, Canada and France, joined international human rights groups in questioning the conclusions of authorities about the fate of the students.
Attorney General Jesus Murillo Karam declared last month that he had the "legal certainty" that the aspiring teachers were murdered in the southern state of Guerrero in September.
Murillo Karam said evidence proved the 43 young men were abducted by corrupt police and delivered to drug gang members who killed them, incinerated their remains in a landfill in the town of Cocula and dumped them in a river.
The Argentine team, which was hired by the parents of the students and has worked alongside federal investigators, said it did "not exclude the possibility that some of the students met the demise" described by prosecutors.
"However, in our opinion, there is no scientific evidence to that effect at the Cocula landfill," the team said in a 16-page statement.
Human rights groups have also 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.
Parents of the students have refused to believe their sons are dead, saying they do not trust the authorities.
- Charred remains -
Officials sent 17 sets of charred bones to Austria's Innsbruck University, but the world-renowned lab was only able to confirm the identity of one student and indicated that the rest of the remains were nearly impossible to identify.
The Argentine experts said they found anomalies in 20 of the 134 genetic profiles of relatives that were sent to the university by the attorney general's office.
The team also provided pictures showing that several fires have burned at the Cocula landfill since 2010, meaning physical evidence collected at the site could belong to other events unrelated to the case.
Among the samples collected by prosecutors was a denture with a tooth, even though none of the students used one.
The Argentine investigators said they found evidence "strongly suggesting the possibility" that the area of the fire contains human remains that do not belong to the students.
The experts complained that after the discovery of the remains the landfill was left open to the public for three weeks, which could taint some of the evidence.
The forensic team said much of the landfill still needs to be investigated and the work will take several more months to complete.
"The investigation cannot be concluded as long as an important quantity of evidence still needs to be processed" by prosecutors and the Argentine team, the statement said.