Independent investigators, who this Sunday ended their work in Mexico, issued a scathing report on the disappearance of the 43 Ayotzinapa students, accusing the government of obstructing their probe and questioning the role of federal forces in the tragedy.

After a year-long investigation ending this month, the foreign experts from the Inter-American Commission on Human Rights, or IACHR, were unable to resolve a case that has shocked the international community and sparked protests against President Enrique Peña Nieto.

While the mystery remains, the report calls for investigations into the conduct of federal police and the military on the night of Sept. 26 and 27, 2014, when the 43 students vanished in the city of Iguala, southern Guerrero state.

The experts also invoked allegations of torture against as many as 17 of the more than 100 suspects detained in the case.

But part of the 605-page report -- the second of their mission -- is dedicated to the "obstructions" that the experts faced from the authorities and which became worse from January.

The authorities showed "little interest" in moving forward with new lines of investigation and it was "impossible" for the experts to reinterview 17 suspects in prison, the report said.

Prosecutors say the students were attacked by municipal police after the young men stole five buses that they planned to use for a future protest. Three students and three bystanders were killed on the spot.

The officers then handed over 43 students to the Guerreros Unidos drug gang, which killed them and incinerated their bodies at a garbage dump in the nearby town of Cocula, according to the government's account.

The experts, who also proved the army and other federal forces were well aware of the fate the students were facing, also reiterated on Sunday that there was no scientific proof that an immense fire took place at the landfill, as the Mexican government continues to insist on this conclusion.