The polygamist sect raided by authorities two months ago has its children back. But with a criminal investigation under way into allegations of sexual abuse, the splinter group's troubles are not over.

Child-welfare officials have alleged that members of the sect pushed underage girls into marriages with older men, and while the last of 440 children seized from the ranch were returned to their parents Wednesday, prosecutors could still bring criminal charges.

"There have been criminal problems located out there," said Schleicher County Sheriff David Doran, who was with state troopers and child welfare authorities when they raided Yearning For Zion Ranch in west Texas on April 3.

The Texas Department of Public Safety and the attorney general's office have taken over the criminal investigation at the request of authorities in the rural ranching community. While they confirm they are investigating, neither will say how long the investigation may take.

Obtaining the DNA evidence and the testimony necessary to prove such a case could prove difficult.

DNA evidence acquired in the custody case is off limits to criminal investigators unless child welfare investigators find wrongdoing or law enforcement gets court permission, and a prosecution probably would go nowhere without at least one willing witness in the insular ranch community. Members of the Fundamentalist Church of Jesus Christ of Latter Day Saints had a strong distrust of outsiders even before all the children at the ranch were taken away.

Child-welfare officials had said that 31 teenage girls at the ranch were pregnant or had had children, but nearly all those the mothers turned out to be adults.

No more than five minors who are pregnant or have given birth were identified during the child custody hearings. Under Texas law, girls younger than 17 generally cannot consent to sex with an adult.

Children from the ranch were allowed to leave foster care after a judge bowed to a Texas Supreme Court ruling last week that the state overreached by taking all of them even though evidence of sexual abuse was limited to five teenage girls. Half the children taken from the ranch were no older than 5.

All 440 children were returned to parents by Wednesday, Child Protective Services spokesman Patrick Crimmins said.

The high court ruling and state District Judge Barbara Walther's orders returning the children do not affect the criminal investigation, which involves several trailer loads of documents confiscated during a raid lasting nearly a week. Authorities removed all documents and photos they say might show relationships between underage girls and older men.

"It's going to take awhile. With any criminal case we investigate, we do as much as we possibly can before turning the case over to the prosecutors," said public safety spokeswoman Tela Mange.

Last week, investigators from the attorney general's office took DNA from Warren Jeffs, the jailed prophet of the FLDS church, saying they were looking for evidence of relationships between Jeffs and four girls ages 12 to 15.

At a custody hearing, state attorneys introduced a photo they said was a wedding picture showing Jeffs embracing a girl and kissing her on the mouth.

Jeffs has been convicted in Utah as an accomplice to rape in the marriage of an underage sect member. He faces similar charges in Arizona, though no trial date has been set.

Authorities have DNA from all the children and many of the parents at the YFZ Ranch — 603 samples in all — but those results cannot be used by law enforcement without a finding of wrongdoing by child abuse investigators or a court order because they were taken from parents and children as part of a civil custody case, not with a criminal search warrant.

Even if the DNA shows children were born to underage girls and adult men, any prosecution will probably be difficult unless a victim testifies.

Utah successfully prosecuted three FLDS members and got a no-contest plea from Jeffs after years of investigation, but Arizona authorities have had to drop some charges because the victim quit cooperating.

Without a victim's testimony, it's impossible to establish jurisdiction for prosecution, a key element that has prevented some charges of members who frequently move among the sect's residences in Arizona, Utah, Texas and elsewhere.

In any sexual assault case, it can be difficult to persuade victims to assist in prosecutions, but such cases are even more challenging when they involve a community as insular as the FLDS, said Paul Murphy, a spokesman for the Utah Attorney General's Office.

Sect members are raised and work within the community, developing few financial or personal resources away from other members.

Texas authorities raided the YFZ Ranch after three calls to a domestic abuse hot line, purportedly from a 16-year-old mother who said she was being abused by her middle-age husband. The calls — which Doran said continued even after all the children were removed from the ranch — are now being investigated as a hoax.

The children and their mothers were taken to a shelter in San Angelo, where they were later separated. E-mails obtained by The Dallas Morning News under Texas public records laws show state officials had proposed sending them to another location because of fears of violence. A judge rejected conducting the separations in Midlothian, and the children were taken from their mothers without incident.

The e-mails also showed state officials' concerns that some of the mothers were planning a "run" from the shelter before they were separated, something FLDS elder Willie Jessop called absurd.

"We never, never did anything other than to comply and to endure what they put us through," he told the newspaper in a story published Wednesday.

The FLDS, which believes polygamy brings glorification in heaven, is a breakaway sect of the Mormon church, which renounced polygamy more than a century ago. Jessop said this week that the church would not preside over marriages between sect members who were not of legal age.

He sidestepped questions about whether such marriages ever occurred but has said the sect has been unfairly portrayed.