A Texas judge has ordered that all the 416 children removed from a polygamous sect recently shall remain in state custody for now. Menatime the children will undergo DNA tests.
Welfare officers had told the judge they had been unable to determine which parents the children were related to.
The ruling comes after officials said some of the girls might have had babies when they were just 13 years old.
The closed community was first raided amid reports that a 16-year-old girl was physically and sexually abused.
Detectives are looking for evidence of a marriage between the girl and a 50-year-old man.
She is reported to have been beaten and raped by her older husband and to be pregnant again eight months after giving birth to her first child when she was 15.
The legal age of sexual consent in Texas is 17.
The girl has not yet been identified, but all children living on the isolated Yearning for Zion ranch aged between six months and 17 years of age were placed in emergency state custody.
Group members live in large extended families, and the sect has been accused of forcing young girls into polygamous marriages, a claim it denies.
Child protection officials said group members were evasive when questioned, making it hard to determine exact parenthood, and that DNA testing was necessary.
Child Protective Services supervisor Angie Voss, testifying in Friday's custody hearing, told the court there was a "culture of young girls being pregnant by older men" at the YFZ ranch.
Voss said the girls were in danger of sexual abuse and the boys were being "groomed" to become perpetrators, AFP news agency reports.
An expert on children in cults told the court that the girls might have believed that marrying much older men was their free choice because they had been raised in that belief.
"Obedience is a very important part of their belief system," said Bruce Perry.
Although many of the adults and children at the YFZ ranch seemed emotionally healthy, the sect's belief system was "abusive", he added.
"The culture is very authoritarian."
The Fundamentalist Church of Jesus Christ of Latter Day Saints sect is led by polygamist Warren Jeffs, who is currently in jail as an accomplice to rape after he forced a 14-year-old girl to marry her cousin.
The self-proclaimed prophet is currently awaiting trial in Arizona on charges of being an accomplice to four counts of incest and sexual conduct with a minor stemming from two arranged marriages.
Members of the sect have denied the latest allegations of abuse.
"It's the furthest thing away from what we do here," said Dan, a sect member.
"There's nothing that's more disliked and more trained against," he added.
The 10,000-strong sect, which dominates the towns of Colorado City in Arizona, and Hildale, Utah, split from the mainstream Mormon church more than a century ago.
Members believe a man must marry at least three wives in order to ascend to heaven.
Women are meanwhile taught that their path to heaven depends on being subservient to their husband.
Polygamy is illegal in the US, but the authorities have reportedly been reluctant to confront the FLDS for fear of sparking a tragedy similar to the 1993 siege of the Branch Davidian sect in Waco, Texas, which led to the deaths of about 80 members.
As a result of the raid, all children on the ranch aged between six months and 17 years of age were placed in emergency state custody.
Texas law states that if sexual abuse is happening in a home and a parent does not put a stop to it, then the parent can lose custody of the child.
One of the judge's tasks is to determine whether or not the ranch constitutes a "home" under state law.
In making her judgement, she may also weigh up the dangers of placing children who have grown up in such an isolated location into mainstream society.
The unprecedented size of the case is also putting pressure on the state's child services division, and if the state is granted permanent custody of the children, it will have difficulty finding foster homes for all of them.
Except for 27 adolescent boys, all of the children are being held in a domed coliseum on land used for the San Angelo state fair. BBC says.