ELDORADO, Texas—Women and girls in prairie dresses entered a courthouse surrounded by dozens of law enforcement officers in this tiny ranching hamlet Wednesday as a grand jury opened its investigation into a polygamist sect accused of forcing underage girls into marriage and motherhood.

The main square in Eldorado was cordoned off with yellow police tape. A sheriff’s department worker snapped photos of anyone who stood by or attempted to talk to sect members who arrived at the courthouse Wednesday and may be grand jury witnesses.

One witness subpoenaed to testify is a 16-year-old girl who denies state claims that she was married off at 15 and had a child soon after. She has asked for a new lawyer, claiming her court-appointed lawyer is lying about her.

Grand jury proceedings are supposed to be secret, but news of the meeting and the girl’s subpoena have been disclosed in other court proceedings related to one of the largest custody cases in U.S. history. The girl is a daughter of Warren Jeffs, considered a prophet by members of the Fundamentalist Church of Jesus Christ of Latter Day Saints.

The girl and her mother said in a brief interview with The Associated Press they were told law enforcement would be testifying in the morning. They came back in the afternoon for possible testimony.

“I don’t want to do it,” said the girl, shuffling her feet under a dark blue pioneer dress.

She said she doesn’t know what she’ll be asked. Her mother added, “We just kind of wonder what it’s all about.”

The Associated Press does not generally identify alleged victims of sex abuse.

The girl had a light moment as she waited at a picnic table outside the courthouse with several other young female FLDS members. She persuaded the others to help pull the table over to a large live oak tree, which she scrambled up to a height of about three stories while the others snapped photos with their cell phones and laughed.

The girl’s attorney, Natalie Malonis, won an extension of a restraining order against FLDS elder Willie Jessop at a hearing Tuesday. Malonis claims Jessop is influencing the girl to be uncooperative, an accusation he denies.

Malonis was subpoenaed to testify before the grand jury, according to a lawyer for the girl’s mother, and the lawyer could be seen coming in and out of the courthouse on Wednesday, as could Texas Rangers, the investigative arm of state police.

The criminal case follows state child welfare officials’ ill-fated April seizure of more than 400 children at the Yearning For Zion Ranch in Eldorado. The children were scattered across foster-care facilities around the state.