DNA tests confirmed the identity of one of the five kidnapping victims, the Attorney General's Department said, while tattoos, surgical markings and dental records enabled authorities to identify the other four.
It is anticipated that DNA testing will soon be completed on all 13 bodies found in the grave for 100 per cent certain identification, the department said.
The bodies were found on a private ranch in an area known as Tlalmanalco, about 50 kilometres southeast of Mexico City. The Attorney General's Department said earlier this week that agents had received information about possible illegal weapons on the property, known locally as Rancho La Negra, and that agents obtained a search warrant.
When they started looking around, they discovered the grave, as well as a 9-millimetre handgun, a shotgun, handcuffs and a bulletproof vest.
The mass grave was covered in a slab of cement and asbestos, while the corpses had dirt and lime poured on them. A federal official who helped discover the bodies said the heads were severed, in what could be a frightening echo of the brutal mutilations of drug cartel victims in other parts of Mexico. The official spoke on condition of anonymity because he was not authorized to discuss the ongoing investigation.
Kidnapped in daylight
The young bar-goers vanished from outside Heaven, an after-hours club, at about 10 in the morning on May 26. The club is located just a block from Mexico City's leafy Paseo de Reforma, the capital's equivalent of Paris's Champs-Élysées, and is near federal police offices and the U.S. Embassy.
Surveillance cameras showed several cars pulling up to the club and taking the victims away.
Prosecutors have said the abductions from the bar were linked to a dispute between an established drug gang and an upstart rival gang, one of which is from Mexico City's dangerous Tepito neighbourhood. The area was home to most of the victims.
The families of the disappeared say the missing young people were not involved in drug trafficking, though there is evidence that some of their relatives were.
So far, five people have been detained in what the Mexican media are calling "el caso Heaven" (the Heaven case), including club owner Ernesto Espinosa Lobo, who has been charged with kidnapping. Among the arrested are another bar owner, a driver and security guard.
The kidnapping and likely murder has revealed a gangland battle for control of the lucrative drug trade in the poshest bars and nightclubs of a megalopolis that had been an oasis of calm during Mexico's nearly seven-year drug war. The head of Mexico City police on Saturday deployed more officers and a helicopter to some of the city's upscale districts along with the rough neighbourhood of Tepito, fearing retaliatory attacks.