In the desert outside Albuquerque, hikers have sometimes stumbled upon human remains partially buried under the hardy scrub and hard-baked dirt.

But few people could have imagined the crime scene now emerging: The bones of at least 13 people have been uncovered on the site of an abandoned housing development.

The grisly discovery last month caused authorities to reopen dozens of cold cases involving missing prostitutes, some of whom vanished as much as 20 years ago.

Since the bones came to light, forensic experts, detectives, anthropologists and medical investigators have raked tediously through mounds of dirt for the next sliver of bone or clump of human hair.

Police believe one person or group of people is responsible for the slayings, but they have been reluctant to make comparisons to any existing serial murder cases.

"We don't want to limit our investigation," Police Chief Ray Schultz said, calling the scene "one of the largest and most complex" ever investigated by his department.

So far, only two sets of remains have been identified. But detectives are reviewing cases involving dozens of women who vanished from the city over the last two decades. All of them were suspected of being drug addicts and prostitutes. Of particular interest are 16 women reported missing between 2001 and 2006.

The two bodies identified so far were Michelle Valdez and Victoria Chavez, both women who disappeared within months of each other in 2004.

Chavez was about 28 when she vanished, leaving behind a daughter. Valdez was 22, with two children and another on the way.

Valdez's mother, Karen Jackson of Myrtle Beach, South Carolina, said her daughter struggled with addiction and worked as a prostitute during periods when she would disappear without any explanation. But she would always resurface to get a hug or money from her father, share a laugh with her sister or call her mom.

Valdez's body and that of her fetus were unearthed Feb. 23. No cause of death has been determined.

Jackson said she was devastated to learn her daughter's fate after years of silence and searching.

"I wanted closure, but not this," she said. "My heart goes out to the rest of the families of the missing women."

The family of Leah Peebles, who is on the list of 16 missing women, is devastated by the discovery but holding out hope.

"I don't think she's out there. I really don't," Peebles' mother, Sharon Peebles, said from her home in Texas. "I have fear and start worrying ... but until I hear otherwise, I feel she is alive."

Leah Peebles, 24, moved to Albuquerque just months prior to her disappearance. She was trying to start a new life free of drugs and the history of sexual molestation and assault that haunted her in her hometown. Her parents reported her missing in May 2006.

The first remains were discovered Feb. 2, when a woman walking her dog found a human rib bone on the site of a subdivision under construction.

The area had been abandoned when homebuilder KB Home ended its operations in New Mexico, leaving a cinderblock wall surrounding mounds of dirt, a drainage pond and a few retaining walls.

Before construction crews left the site in early 2008, many of the bones were damaged by earth-moving equipment that scattered the remains across 100 acres surrounding the concentrated burial site.