(CNN) -- Authorities said Monday they have taken legal custody of 401 children who lived on an isolated West Texas polygamist retreat built by imprisoned "prophet" Warren Jeffs.
The children are being kept at a temporary shelter at historic Fort Concho in nearby San Angelo while authorities investigate whether a child bride gave birth on the ranch at age 15.
The children in state custody are joined at the shelter by 133 women, most of them mothers, who were taken during the past few days from the sprawling Yearning for Zion ranch, said Marleigh Meisner, a spokeswoman for the state's Child Protective Services agency.
The women are free to return to the 1,900-acre compound, officials said, but many have chosen to remain. At this point, officials said, the children's fathers are not permitted to see them.
Court proceedings began Monday to determine whether there is enough evidence to remove the children from their homes on the ranch, which is near Eldorado, Meisner said. A hearing is scheduled April 17.
The children will be appointed lawyers and legal guardians in about two weeks, she added.
Meisner said the temporary shelter is filling up quickly, and officials are facing a "critical shortage" of foster homes. Officials will try to keep siblings together, she added.
Law enforcement officials would not provide many details of their investigation, but Meisner said the 401 court affidavits being filed Monday should shed some light on the alleged abuse.
The investigation, which began Thursday night, is continuing and authorities remain on the property to search for evidence and other children, said Tela Mange of the Texas Department of Public Safety.
One man has been arrested, allegedly for interfering with investigators. He faces a misdemeanor charge, authorities said.
Investigators said they believe more children will be found at the ranch, but Mange stopped short of saying they were being hidden.
Authorities would not say whether they have located or identified the teen tipster whose call prompted the raid.
On March 31, a 16-year-old called and reported physical and sexual abuse on the ranch, authorities said. She said she was married to a 50-year-old man. Authorities are looking for evidence the girl had a child at the age of 15.
It remains unclear whether the girl who reported being abused is among the children being interviewed -- or was whisked away from the compound under a different name before authorities arrived.
"I am confident that this girl does indeed exist," Meisner said earlier. "I am confident that the allegations that she brought forth are accurate."
One issue compounding an already difficult and sensitive investigation is the difficulty pinning down exact names and ages of the people being interviewed -- as well as of the people being sought.
The Fundamentalist Church of Jesus Christ of Latter Day Saints bought the ranch four years ago and began erecting dormitories and a large, white temple. Hundreds of Jeffs' followers moved from Arizona and Utah as authorities there stepped up their investigations.
The name is taken from one of Jeffs' spiritual songs, "Yearning for Zion."
Authorities began blocking roads to the YFZ ranch Thursday, then raided the compound and began busing women and children off the property. Most were girls, and most wore hand-sewn prairie dresses.
Officers entered the compound with a search warrant for 50-year-old Dale Evans Barlow, who they believed was married to the 16-year-old tipster. The search warrant authorized law enforcement to seize any evidence of a marriage between the two including CDs, DVDs and a computer hard drive, The Associated Press reported.
Barlow was sentenced to jail last year after pleading no contest to conspiracy to commit sexual conduct with a minor, the AP said.
Barlow was ordered to register as a sex offender for three years while on probation, the wire service reported. Barlow's probation officer, Bill Loader, told The Salt Lake Tribune in Utah that he was in Arizona and did not know his accuser.
It remained unclear, the spokeswomen said, whether that was the same Dale Barlow named in their warrant. They acknowledged the man they are seeking might not be in Texas, but said they had no other details about his whereabouts.
CNN's previous visits to the ranch revealed the compound was guarded by armed men equipped with night-vision gear and other high-tech surveillance tools.
Authorities would not say Monday whether they had found any weapons.
Jeffs remains jailed in Kingman, Arizona, where he awaits trial on four counts of incest and sexual conduct with a minor stemming from two arranged marriages between teenage girls and their older male relatives.
Jeffs was sentenced in November to two terms of 5 years to life for being an accomplice to the rape of a 14-year-old girl who said she was forced to marry her cousin.