The children removed from a polygamist sect last month amid fears of underage sexual abuse could be returned following a court ruling.

The latest twist in the largest custody case in American history means that the 463 children may soon be reunited with their families, having been initially sent to foster care centres across Texas.

The court in Austin, Texas, ruled today that there was insufficient evidence of an immediate threat being posed to the physical health or safety of the children, who had been removed from Yearning for Zion, a polygamist ranch of the Fundamentalist Church of the Latter Day Saints (FLDS) near Eldorado, Texas.

It came before any decision on the case itself had been made, but followed an application by 38 women who challenged state custody and a further 54 who filed a second action. Many of the women were at the court, wearing long traditional dresses.

"It's a great day for Texas justice," Julie Balovich, a lawyer for some of the women, said after the ruling was announced.

The court declared that children could only be taken in this way if there was an immediate threat posed to their physical health or safety. It said the State of Texas Department of Family and Protective Services, which had made the order for the children to be taken into state custody, had failed to establish the existence of such a threat.

The Texas ranch was raided on April 3 after a call was made to an abuse hotline. The caller said she was a 16-year-old child bride being abused by her older husband in the church's compound. She has still not been identified.

State officials had argued the raid was legitimate and that taking the children had been necessary, since the sect's culture led to illegal under-age marriage for girls, and to acceptance of that practice for boys.

"There is a culture of young girls being pregnant by old men," Angie Voss, an investigator with Child Protective Services, said in the context of an earlier court hearing. Miss Voss said she had discovered evidence that "more than 20 girls, some of whom are now adults, have conceived or given birth under the age of 16 or 17."

The state had initially said that as many as 31 girls in their custody were underage and were either pregnant or already had children. At follow-up hearings this week it admitted that 15 of the girls are over the age of 18.

Warren S Jeffs, the current FLDS leader, was convicted on a rape charge in 2007 for forcing an under-age girl to marry an older man in Utah.The FLDS split from the mainstream Mormon church in 1890 when the Mormons disavowed polygamy.

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