Authorities in the Mexican border city of Ciudad Juarez said Wednesday that they plan to exhume the remains of more than 4,000 unidentified people buried in common graves and take DNA samples in an attempt to identify them.

Rene Medrano, a spokesman for the Chihuahua state attorney general's office, said the bodies were being exhumed because state attorney general Patricia Gonzalez "wants to bring order and clarity to past police practices."

Officials did not provide more exact reasons for the exhumations, which they called part of a statewide project that includes at least 180 exhumations in another city.

Authorities said the project was not directly related to the cases of 360 women killed over the past 14 years in Ciudad Juarez, a city of 1.3 million across from El Paso, Texas.

Victims' relatives have long demanded that independent investigators take part in the probes, saying efforts by state officials have been tainted by inept officers. Chihuahua state investigators have been accused of losing or contaminating evidence and of other missteps that botched cases.

Authorities' lack of progress in solving the cases of the Ciudad Juarez women prompted international outrage, as news of the killings made headlines around the world.

Authorities have arrested and prosecuted a number of suspects over the years, but family members of some Juarez victims say authorities have yet to bring the true culprits to justice.

Federal authorities intervened in 2003, promising to solve 14 rape-strangulation cases involving teenagers and women in Ciudad Juarez. The federal attorney general's office recently closed those investigations, however, without getting to the bottom of what happened.

A team of 30 people, including forensic anthropologists and dental specialists, are already exhuming remains from cemeteries in Ciudad Juarez, Medrano said.

The team will exhume unidentified bodies that were buried in common graves between 1991 and 2005, Medrano said. They will extract DNA samples and build a database. The remains then will be tagged and reburied in individual graves, he said.

Officials estimate more than 4,000 unidentified bodies were buried in common graves in Ciudad Juarez alone over the 14-year period.

The program first started three months ago in Chihuahua City where authorities exhumed 180 sets of remains. One already has been identified, Medrano said.