Members of the sect deny abusing their children
Custody hearings have begun in a case involving parents of 463 children taken from a polygamist sect in western Texas following allegations of sexual abuse.
The hearings will allow parents seeking to regain custody to make their case.
In April, officials raided a compound of the sect saying young girls were being forced into marriage and sex. The children were placed into foster care.
The Fundamentalist Church of Jesus Christ of Latter Day Saints has denied abuse and says it is being persecuted.
So far, 168 mothers and 69 fathers of the children have been identified - reflecting the polygamist practices of the sect - the Associated Press news agency reports.
More than 100 children have still not been matched with mothers
The hearings, in the town of San Angelo, are expected to take several weeks.
The Texas child welfare authorities have drawn up action plans outlining the steps the parents must take to regain custody of their children.
These include parenting classes and psychological testing, and require parents to show they can support their children and give them a safe living environment.
Parents and their lawyers said the plans were unclear, leaving them without answers to key points, AP quoted them as saying.
"This plan is so vague and so broad that my client has no idea what she can do now," said lawyer Donna Guion, representing the mother of a six-year-old son of the sect's jailed leader, Warren Jeffs.
The FLDS members say they are being persecuted for their religion.
Some of the parents say they do not know where their children have been placed, while others have complained that their sons and daughters are living at different locations, forcing them to criss-cross Texas to see them.
AP says the case, which began with a raid on 3 April, has been marked by confusion.
The children were taken from the sect's Yearning For Zion ranch
Officials have said that at least four of the sect members they had listed as minors are in fact adults.
They said the situation was complicated because some women and children had given different names and lied about ages.
The authorities have said that all the underage children needed to be removed from the ranch because the sect forced underage girls into marriage.
Initially, officials said more than half of the underage girls were either mothers or were pregnant.
The legal age of sexual consent in Texas is 17 and polygamy is illegal in the US.
The children were removed from the Yearning For Zion Ranch in Eldorado after someone called a domestic abuse hotline claiming to be a pregnant 16-year-old abused by a much older husband.
The girl has never been found and authorities are investigating whether the calls were a hoax.
Earlier this month, investigators said they had found signs of physical injuries among the children, but added it was unclear whether these were due to abuse.
Members live in large extended families, making it hard to determine exact parenthood, and the state is using DNA tests in its investigation.
The Fundamentalist Church of Jesus Christ of Latter Day Saints (FLDS) is an offshoot of the Mormon Church, from the mainstream Mormons more than a century ago.
FLDS members are taught that a man must marry at least three wives in order to ascend to heaven.
The church denies forcing young girls into polygamy.