Texas child welfare officials conceded Tuesday that a newborn's mother, held in foster care as a minor after being removed from a polygamous sect's ranch, is an adult.

A Child Protective Services attorney told state District Judge Barbara Walther that the mother of a boy born April 29 is not a minor, as CPS had claimed as justification for holding her.

The woman had been held along with more than 400 children taken last month from a west Texas ranch run by the Fundamentalist Church of Jesus Christ of Latter Day Saints. State officials say the children were endangered by underage and polygamous spiritual marriages.

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"We were presented with credible evidence that this minor is, in fact, an adult," said CPS spokeswoman Marleigh Meisner.

She declined to say what the evidence was or how old the woman is. According to FLDS records, the new mother, Pamela Jeffs, is 18.

She was one of two pregnant sect members who state officials had said were minors. The other sect member, who gave birth to a son Monday, also may be an adult, state officials have said.

Both mothers are with their babies, who are in state custody.

CPS has complained that sect members have given different names and ages, confusing the identification process in one of the largest, most convoluted custody cases in U.S. history.

But FLDS spokesman Rod Parker has accused the state of holding on to pregnant women and treating them as minors to ensure the state could take custody of the newborns, who might otherwise be born outside of Texas. A call to Parker was not immediately returned Tuesday.

There are 27 claims of women being misidentified as girls when they were taken into state custody from the Yearning For Zion Ranch in Eldorado. If evidence is provided proving they are not minors, they will be released, Meisner said.

"We are still in the midst of an investigation. We continue to speak with the children, parents and others who have information that would be helpful to us," she said. "We cannot just dismiss these cases without credible evidence regarding their ages. We have an obligation to protect children."

The state's admission on Tuesday takes the total number of children in state custody down to 464.

Texas child welfare authorities took the children into custody on the argument that the polygamist sect abused children by pushing underage girls into marriage and sex and by raising boys to be future perpetrators. FLDS members have denied any abuse.

All the children are expected to get individual hearings starting May 19.