SAN ANGELO, Texas—Five men from a polygamist sect raided by Texas authorities in April stand accused of sexually assaulting children, but they’re unlikely to be the only ones.

Church documents disclosed as part of a separate child custody case over the last several months identify at least 10 other men as married to girls who were 16 or younger. The girls’ fathers and stepfathers blessed the unions and sometimes presided over ceremonies between other young girls and adult men, the documents show.

In all, about 20 underage girls, a few as young as 12, are identified in the documents as married to jailed sect leader Warren Jeffs or one of his followers.

Underage marriages were not universal within the Fundamentalist Church of Jesus Christ of Latter Day Saints, but the marriage certificates, Jeffs’ journal entries, photos and family listings show they were not—as the church suggested early on—isolated events either.

“We didn’t really have a sense of what was going on out there. We knew there was a potential for a problem,” said Schleicher County Sheriff David Doran, who visited the Yearning For Zion Ranch in the years before the raid. “The state has that evidence now, or I believe they do.”

Over six days in April, Texas authorities collected more than 400 boxes of documents from the West Texas ranch, rifling through homes, offices and the towering limestone temple for evidence of girls forced into underage marriages and sex.

Officials from the Department of Public Safety and the Attorney General’s Office, which is overseeing the prosecutions, will only say that the investigation continues.

The Schleicher County grand jury that indicted five FLDS men on sexual assault and a sixth for failing to report abuse is scheduled to meet again Thursday.

Grand jury proceedings are secret, but documents in the separate child custody case, filed over the last several months, show even men who have not been charged with abuse married girls who were 15 or 16 in church ceremonies. Most of the men were in their 20s and 30s.

Four younger girls, ranging in age from 12 to 14, are shown in marriage certificates, photos and notes as married to 52-year-old Jeffs, who was convicted in Utah as an accomplice to rape for the marriage of a girl to her older cousin.

“I’m praying to become a heavenly comfort wife for you ... I feel so close to you,” reads one note from a 12-year-old to Jeffs. Church records show she married him three months before.

Jeffs is among five charged last month in Texas with sexual assault, but he first faces charges in Arizona, where he is currently jailed.

Under Texas law, girls younger than 17 generally cannot consent to sex with an adult.

Being married to more than one person or even “purporting” to be married to more than one person is also illegal. Texas investigators early on were working about 50 possible bigamy cases.

Rod Parker, a Utah attorney and spokesman for the church, said he believes the practice of underage marriages was “relatively limited” and continues to believe FLDS members have been unfairly treated by Texas authorities.