Parents of the 43 Mexican students who went missing last year insisted they would “not allow this case to be closed” after Attorney General Jesus Murillo Karam said he was certain all of them were dead.

Mr Murillo said on Tuesday that confessions and forensic evidence showing a fire had blazed for hours “at a temperature sufficient to turn 43 bodies into ashes,” combined with remains found in bags dumped in a river with “traces” from the same fire, proved the students had been killed and incinerated.

The confession was based on the testimony of a suspect who says he was called to “get rid of” the students. Ninety-nine people have so far been detained in connection with the massacre, including former mayor of Iguala Jose Luis Abarca.

The attorney general added that the army did not either “participate in or allow” the killings — contradicting claims from the victims’ relatives.

But parents responded with a news conference in which they accused the government of trying to wrap up the investigation.

“We don’t believe anything of what they say,” said Carmen Cruz, whose 19-year-old son Jorge is among the missing.

Their lawyer Vidulfo Rosales presented a 10-point argument explaining why the investigation had to continue.

DNA tests had only been able to identify one of the students, he pointed out, and a number of key suspects remain at large.

Their testimony could shed light on whether the official conclusion — that police arrested the students and then handed them over to members of a drug cartel who killed them — is accurate.