US authorities handed over a key suspect in the 2014 disappearance of 43 college students to Mexico, after the man was caught trying to cross the border on December 20 without proper documents.

Mexico’s National Immigration Institute identified the man only by his first name, but a federal agent later confirmed on Thursday that he is Alejandro Tenescalco. The institute said he failed to qualify for asylum in the United States.

Tenescalco was a police supervisor in the city of Iguala, where the students from a rural teachers’ college were abducted by municipal police. Investigations suggest corrupt police turned the students over to a drug gang, who killed them and burned their bodies.

Alejandro Encinas, the head of the government Truth Commission, has called Tenescalco “one of the main perpetrators” of the crime.

He faces charges of kidnapping and organised crime. The Mexican government had offered a 500,000 dollars (£404,000) reward for his arrest.

In 2022, the Truth Commission declared the disappearances a “state crime” because authorities at all levels of government were involved in the disappearances and cover-up.

The investigations resulted in the arrests of three soldiers, including a now retired general who had been the army commander in the area when the abductions occurred.

Also, then federal Attorney General Jesus Murillo Karam has been accused of inventing the government’s original account based on torture and manipulation of evidence.

But some charges against dozens of other suspects have been thrown out because of tainted evidence.