Mexican authorities are seeking permits to exhume the remains of the parents of Heriberto Lazcano to obtain material for DNA testing in order to convince the public beyond doubt that the drug lord is dead.
"We were trying to track down the relatives [of Heriberto Lazcano, deceased Zetas drug cartel leader]," said Jose Cuitlahuac Salinas, Mexico's Assistant Attorney General, on Wednesday.
Lazcano's body was stolen by a team of armed, masked men from a funeral home in northern Coahuila state early this month, shortly after he was killed the day before, according to officials.
Mexico's navy says Lazcano's body was identified through fingerprints before the corpse was taken. Local prosecutors have said they did not know the body was Lazcano's until after it was stolen.
Salinas said Lazcano's parents died years ago and are buried in central Hidalgo state.
"We're in the process of obtaining the proper permits for the exhumation, so we can get their genetic profile," said Salinas.
"Unfortunately, both parents died many years ago, and that complicates things."
He did not say what sample from Lazcano's body would be used for comparison, but an autopsy was performed before the body was taken and officials apparently saved blood or bloody clothing.
"Unfortunately it hasn't been possible to find the brothers, excuse me, in this case, sisters who are the ones with direct kinship."
The testing is aimed at confirming that a body stolen from the funeral home on October 8 was indeed Lazcano's.
The Mexican Navy says Lazcano's body was identified through fingerprints after he was killed in a shootout with marines on 7 October.
Salinas said on Wednesday that Lazcano's parents died years ago and are buried in central Hidalgo state.
US officials have said they knew that Mexican marines had killed the head of the widely feared Zetas drug cartel before the body was stolen in a pre-dawn raid from Garcia funeral home.
One official says the US independently verified the identity of Lazcano.
The account throws into question the Mexican Navy's insistence that marines left Lazcano's body unguarded because they thought they had killed a common criminal.
Notoriety for brutality
Lazcano "is credited with strengthening the organisation ... he created a new structure of regional cells that specialise in specific crimes", Mexican federal prosecutors say in their profile of Lazcano.
The Zetas earned their notoriety for brutality by becoming the first to publicly display their beheaded rivals, most infamously two police officers in April 2006 in the resort city of Acapulco.
The severed heads were found on spikes outside a government building with a message signed "Z" that said: "So that you learn to respect."
Even with the death of Lazcano, the Zetas would still be run by a ruthless leader, Miguel Angel Trevino Morales, who has a reputation for being even more brutal than Lazcano.
Trevino Morales, also known as Z 40, has taken on a greater leadership role and has even been reported to have replaced Lazcano as operational chief.
More than 60,000 people have died in drug-related violence in Mexico since December 2006, when President Feilpe Calderon put the military in charge of a campaign against organised crime.
Most of the deaths occurred in provinces alongside the Mexican border with the US.