Laboratory tests showed no evidence that Mexico’s missing 43 students were among the remains recovered from a rubbish tip, where the Mexican government insists the teacher trainees’ bodies were burned in an all-night inferno and the ashes tossed in an adjacent river.

The results, released to reporters late Friday night, dealt further discredit to the official investigation, which the attorney general at the time called “the historic truth”. The report comes after the Mexican government defended its original inquiry from accusations that it undermined the work of international investigators, who considered the fire theory implausible and scientifically impossible.

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“These results do not scientifically support the attorney general’s office theory,” said Mario Patrón, director of the Miguel Agustín Pro Juárez Human Rights Centre, which was worked with the students’ families and the international investigations into the case.

“It was not possible to obtain, at this point, identifications of the genetic profiles in all the samples of skeletal remains,” along with other samples of hairs found on clothing, the attorney general’s office said in a statement. The results of one further process of DNA testing is still pending.

The findings from a laboratory at the University of Innsbruck, Austria, were similar to those of experts from the Argentine Anthropological and Forensic Experts, who found 19 human remains in the rubbish dump, but were unable to identify any of the missing students.

Another group of experts, from the Inter-American Commission on Human Rights (IACHR), found weather records registering rain on the night of the supposed fire in September 2014. That team also studied satellite images and found no trace of large fires in the area. No evidence of a controlled burn was found, though the experts said recurring fires – none large enough to burn 43 bodies – were common in the garbage dump.

The Austrian laboratory has previously identified two students from remains that, according to the attorney general’s office, were found in the landfill and a nearby river, some 200km south of Mexico City. The Argentine experts, though, say one of the identifications was inconclusive, while the other came from evidence with questions surrounding its chain of custody.

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Authorities have theorised that corrupt police officers, allegedly acting with organised crime, attacked the Ayotzinapa teaching students while they were on buses en route to a protest in September 2014. They have suggested that the officers then turned the bodies over to criminals, who burned their remains.

The attorney general’s office said in its statement the results of one final DNA sequencing test on the remains are still pending.