By the CNN Wire Staff

updated 12:27 PM EDT, Thu May 17, 2012

Mexican police work the grisly scene where 49 dismembered bodies were found Sunday near Monterrey.

STORY HIGHLIGHTS

Monterrey, Mexico (CNN) -- Mexican authorities are asking for DNA samples from families of missing persons nationwide in their efforts to identify 49 decapitated bodies, an official said Wednesday.

That will be the only way to identify the victims -- whose killers cut off their heads, hands and feet -- Nuevo Leon state security spokesman Jorge Domene told reporters three days after investigators found the remains abandoned along a highway.

Officials in El Salvador may also request access to the DNA data authorities in Nuevo Leon have compiled, to compare it with samples from family members of Salvadoran migrants who have gone missing in Mexico, Domene said.

While investigators work to identify the victims behind closed doors, parts of the case have played out quite publicly.

Banners hanging in locations throughout the country, purportedly from the Zetas, claim that the notoriously ruthless cartel had nothing to do with the gruesome crime.

But another message purportedly signed by the Zetas and found Sunday at the crime scene -- a roadside near the industrial city of Monterrey and about 80 miles southwest of the U.S. border -- told a different story, threatening members of rival cartels and Mexican authorities.

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DNA sought to ID decapitated bodies in Mexico