More than 400 children are now in state custody following last week's police raid of a secretive religious retreat built by polygamist leader Warren Jeffs, Texas authorities said Monday.

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Police escort members of the Fundamentalist Church of Jesus Christ of Latter Day Saints on to a school bus in Eldorado, Texas, on Sunday. ((Tony Gutierrez/Associated Press))

State troopers are investigating allegations that a teenage girl married a 50-year-old member of the community and had a baby with him when she was 15. Such a marriage would be illegal under Texas law, which prohibits girls under age 16 to marry, even with parental approval.

The girl, who is now 16, telephoned police last week, prompting Friday's police raid of the 700-hectare compound in the small town of Eldorado, about 300 kilometres northwest of San Antonio.

Authorities do not know whether the teen is among the 220 children and women initially reported on Friday to have been taken from the retreat to the San Angelo Museum, which is north of Eldorado.

The children had been legally taken into state custody, a move Child Protective Services makes when it believes children have either been harmed or are in imminent danger.

Marleigh Meisner, a CPS spokeswoman, said those taken from the compound are co-operating with authorities.

They boarded buses on Sunday for the San Angelo Museum. Many were wearing long pastel dresses and carrying bedding and infants.

An arrest made Monday

Meisner said the investigation is difficult because many members of the community are related to each other, have similar names and change their names frequently. Ages are also hard to determine, Meisner said.

One person was arrested in connection to the raid on Monday, Tom Vinger of the Texas Department of Public Safety said. Vinger would give no details, except to say that the person is not Dale Barlow, the man accused of marrying the teenage girl.

Prosecutor Allison Palmer said authorities know where Barlow is, and have talked with him, although she wouldn't give more details.

Barlow is on probation after serving time last year for sexual conduct with a minor. He was ordered to register as a sex offender during his three years probation.

Police who are investigating the Eldorado compound have a search warrant that allows them to look for marriage records or other evidence linking Barlow with the teen and her baby.The warrant authorizes the seizure of computer drives, CDs, DVDs and photos.

Sect broke from Mormons

As police search the compound, they are blocking access to the property and surrounding area. The compound sits behind a large hill in Eldorado, with the entire property — except for the top of a 25-metre-tall white temple — shielded from the town's view.

The community is part of the Fundamentalist Church of Jesus Christ of Latter Day Saints, a sect run by Jeffs that broke away from the Mormons after the latter disavowed polygamy more than a century ago.

The sect includes about 1,000 followers in the religious community of Bountiful, B.C.

Jeffs is in jail in Arizona, where he is awaiting a second trial on charges of incest and sexual conduct with a minor.

In November, he was sentenced to two consecutive five-year prison terms for being an accomplice to the rape of a 14-year-old girl who wed her cousin in an arranged marriage in Utah in 2001.

With files from the Associated Press