Forensic teams in Ciudad Juarez in Mexico are unearthing more than 4,000 bodies buried in common graves.
Hundreds of women are missing from town on the US border
A local government official said DNA samples from the bodies would be compared to those of missing persons.
It is thought that some of the bodies could belong to women killed in a wave of unsolved murders that began in the city in 1993.
The official said the corpses were buried in common graves because they had not been claimed after 90 days.
The bodies being exhumed were buried between 1991 and 2005 - all unclaimed bodies buried since 2005 have been identified first.
More than 300 women have been murdered in the town in Chihuahua state since 1993, and an unknown number have gone missing.
There is no generally accepted motive for the killings.
They have been variously attributed to serial killers, drug cartels and domestic violence. Some of the killings are believed to have been sexually motivated.
Many of the victims were poor working mothers employed in factories in the industrial city, which is on the border with Texas.
There have been several arrests, but the killings have continued.