When California police discovered an abused girl covered with scars nearly six years ago, they had no idea that the woman allegedly responsible for inflicting the torture was her mother — the friendly cashier they'd encountered at their local fast-food restaurant.

Greisy Valencia, a smiling Colombian immigrant who greeted law enforcement for years at fast-food drive-thrus in Hayward, Calif., hid a horrible secret, police said.

Hayward Police Sgt. Keith Stiver now describes the cashier as "very uncaring, selfish, cruel and a person with a whole lot of issues around parenting." But officials only learned of her alleged double life when Valencia's secrets began to unravel in December 2002, with the discovery of a disheveled, abused 11-year-old wandering the streets of Manteca, Calif., more than an hour away.

"It almost looked like the girl had scales because of the way the overlapping looping scars were on her back, her buttocks and her legs," Stiver told FOXNews.com. The girl's hair was falling out, a condition called traumatic alopecia, brought on by stress.

Police said her baby sitter had planned to call police about the abuse but the girl wandered away because she wanted to warn her mother the police were coming for her.

"It’s very common for victims of abuse like this to defend the abuser," Stiver said. "She snuck out of the house in an attempt to get back to Hayward to locate mom and warn her the cops were going to be coming."

Investigators believe Valencia physically abused the 11-year-old and her 17-year-old brother for years. A 9-year-old sibling was not abused.

Valencia, by many accounts, had built the American dream for herself and her family in California, becoming a U.S. citizen and holding multiple jobs at fast-food restaurants and earning enough money to bring an undocumented friend north from Los Angeles to help raise the children.

But police say the smiling cashier was brutalizing two of her children, especially the girl, who admitted the abuse to social workers.

"The first thing that she recounted was her hands being burned," San Joaquin County social worker Lise Bachman-Carnes told "America's Most Wanted."

Police said Valencia would take her children only when she felt like being a mom, and that she'd use her undocumented friend as the de facto caretaker between beatings, threatening to take action with the authorities if she reported the abuse.

"It was easy for [Valencia] to represent herself as being a friend to law enforcement and say 'they’ll back me up and you’ll be the one who gets deported if you say anything or do anything,'" Stiver said.

That all changed on Dec. 11, 2002, when the girl accompanied her "stepmother" to Manteca and told officials that her mother, Valencia, had turned on her own flesh and blood.

It heralded a new beginning for the children — the girl needed surgery to correct her scale-like scars — and a life on the lam for Valencia.

"On the day that this case broke," Stiver said, "she borrowed some money from her boss before we knew her connection ultimately — $600 that she borrowed from her boss — and split, telling her boss, 'I’m not sure when I’m going to get back.'"

The children have been permanently placed in a home and are doing well, investigators said, but the trail to their mother, who is wanted on charges of torture, has run cold. Officials believe she may have fled the country.

"It would be very difficult for someone who had spent 20 years weaving their way into American lifestyle to suddenly drop everything — all the resources, the bank accounts, the Social Security number, everything they had developed here — disappear and still remain in the country," Stiver said.

Greisy Valencia, now 54, is described as 5-foot-3, weighing 155 pounds, with white hair and brown eyes. She may dye her hair.

Anyone with information as to her whereabouts is asked to call the Hayward Police Department at (510) 293-7001.

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