Forensic scientists from Argentina are challenging the official account of what happened to the 43 Mexican students who disappeared from the southern state of Guerrero in 2014, the BBC reports. Mexico’s government has maintained that the students were arrested by local police who then transferred them to a local gang that murdered them and burned beyond recognition at a garbage dump on the outskirts of the town of Cocula. After a yearlong investigation, however, the Argentine Forensic Anthropology Team found no DNA belonging to the students at the site.