LUSBY, Md. (AP) -- Child-sized human remains uncovered in a basement freezer were those of two girls and have been there for months, their adoptive mother told investigators. They said Monday they believe she is responsible for their deaths.

Sheriff's deputies were investigating an abuse complaint regarding a third, surviving child Saturday when they discovered the remains encased in ice. The mother told investigators that they had been in her southern Maryland home's freezer for at least seven months, and police said they are considering the case a homicide.

"We have reason to believe that's the two children in the freezer," said Lt. Bobby Jones of Calvert County Sheriff's Office. "We believe that the mother, who adopted the two children, is responsible for it."

Autopsies would need to be completed before authorities know for sure whether it is the girls, who would be 9 and 11. Deputies made the gruesome find in Lusby, about 50 miles southeast of Washington, D.C. They were at the home with a search warrant to investigate what happened to the runaway 7-year-old girl who "showed signs of extreme abuse and neglect," the sheriff's department said.

The girl's mother, 43-year-old Renee Bowman, has been arrested, and a judge has ordered her held without bond. She is charged with first-degree child abuse in the beating of the 7-year-old who was found wandering in the neighborhood wearing only a blood- and feces-soaked T-shirt, authorities said.

"I asked if she was OK. She said no," said neighbor Phillip Garrett, who found the girl walking down the street. "She said, 'My mother beats me to death all the time."'

She escaped from a locked bedroom by jumping out a second-story window, and Bowman admitted beating her with a "hard-heeled shoe," officials said.

Bowman told detectives that she brought the remains of her other daughters with her when she moved in February from Rockville, about 60 miles away. Montgomery County Police said they are investigating whether the deaths took place in Rockville and that detectives are trying to pin down when the older girls were last seen alive. Bowman has not been charged in the deaths.

It is not clear how the older children might have died and the medical examiner's office in Baltimore was examining the freezer and its contents. It was also unclear how long it would take for autopsies to be completed.

Bowman was a foster mother to all three before adopting them in the District of Columbia, officials said at a news conference.

According to charging documents, the youngest girl went door-to-door looking for help Friday night.

The girl had open sores and lesions on her buttocks and lower thighs, marks on her neck made by a cord, rope or other item and bruises on her hands and lips, police said. She told investigators that she jumped out the window to "free herself from her mother's relentless beatings," according to the documents. She is being cared for by child protective services.

Garrett, 21, who lives two houses down from Bowman, said he brought the girl to a neighbor's house, called 911 and ordered her a pizza. She indicated she had last eaten on Tuesday when her father was at the home, said Garrett, who realized he had met her mother once and described her as "frazzled."

"She didn't seem like all her pieces were there," Garrett said.

Later Friday, authorities went to Bowman's modest, single-story house in the secluded, heavily wooded subdivision but nobody was home. Bowman showed up later at the sheriff's office and said she had locked her daughter in the child's bedroom.

She told the deputy who interviewed her about the 7-year-old's abuse "that she knew what she did was wrong," according to the charging documents. "She advised she (Bowman) was out of control and needed help."

Sheriff Mike Evans said the surviving girl was never enrolled in Calvert County Schools and that no trouble had ever been reported at the house. Bowman's only contact with the sheriff's department since she arrived was a traffic stop.

Evans said Bowman had a boyfriend who was cooperating with investigators. The boyfriend was a potential witness, but Evans would not comment on whether he was a suspect. He said the man did not live with Bowman and was not a father to her children.

No attorney had entered an appearance on Bowman's behalf Monday afternoon.

Bowman adopted the oldest girl in July 2001, D.C. officials said. Three years later, she adopted the girl who would now be 9 and her 7-year-old sister. She is not biologically related to them.

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Associated Press writers Gillian Gaynair in Washington and Sarah Karush in Falls Church, Va., contributed to this report.

(Copyright 2008 by The Associated Press. All Rights Reserved.)