Mexican authorities have made some disturbing findings in their search for the reasons behind the mass execution of 43 students, who were recently reported as missing.

Forty-three college students kidnapped by police under orders of a mayor in southern Mexico were probably killed by a drug gang that tried to destroy all evidence of the crime, according to investigators.

Criminal suspects rounded up in the probe said police in Iguala, Guerrero, handed them more than 40 people they had taken into custody, Mexican Attorney General Jesus Murillosaid in a news conference in the capital yesterday. The mayor and his wife are accused of asking drug gangs to help police prevent students from disrupting a public event held by the wife, Murillo said.

Fifteen of the captives died from asphyxiation and the suspects confessed to executing the rest, he said. Members of the Guerreros Unidos drug gang told authorities that they burned the victims’ corpses in a landfill for at least 12 hours, along with their clothes and other belongings, throwing in diesel fuel, gasoline and tires to fan the flames, Murillosaid. They then placed their remains in garbage bags and dumped them in a river.

DNA tests are being conducted to provide conclusive proof of the victims’ identities, Murillosaid.

“The testimonies and confessions that we’ve collected, combined with other investigations, very sadly point to the killing of a large number of people,” Murillo said during an hour-long news conference as he presented the suspects’ videotaped confessions and photographs of human remains. “The high degree of degradation caused by the fire makes it difficult to extract the DNA to allow us to identify the remains.”