Test results of the remains police also found 40 jaw bones and 30 leg and arm bones will be checked against missing person lists
Authorities in the Mexican capital are carrying out DNA tests on 42 human skulls and other remains discovered during a raid on a drug trafficking bolthole in the inner-city neighbourhood of Tepito.
Mayor Claudia Sheinbaum told reporters that the results will be checked against the lists of missing people both in the capital and across the country.
A number of the skulls were found arranged within a kind of altar. Police also seized 40 jaw bones, as well as 30 leg and arm bones, and a fetus in a glass jar.
Photographs distributed by the authorities showed the altar also featured a cross, wooden masks, knives, and a large picture of what appears to be a horned goat in front of a pyramid.
The find is not necessarily an indication of murder in a country where popular culture provides for a vast range of different relationships with the dead.
All over the country people flock to cemeteries during Day of the Dead celebrations around 1 November to decorate, and often party, over the graves of their loved ones.
In the indigenous Mayan community of Pomuch, in the southern state of Campeche, the tradition includes families digging up the bones of their relatives and giving them a clean.
The fascination generated by the drug den altar in Tepito may also offer a diversion from the controversy surrounding the massive pre-dawn raid in which it was discovered. Hundreds of police and marines participated in the operation which uncovered two suspected methamphetamine labs, as well as 2.5 tons of marijuana, 20 guns, five grenades, and a rocket launcher.
But hopes that the raid represented a major blow to a local trafficking gang known as La Unin crumbled when a judge released 27 of the 31 people arrested. He argued that the case against them was full of irregularities, including video evidence that many of those detained were actually at a party at an entirely different location from where police said they had been arrested.
Mexican authorities are under intense pressure to prove that they can combat organized crime after a string of high-profile security disasters, including the murder of 13 police officers in an ambush, and the brief capture and release of a son of Joaqun El Chapo Guzmn.