Jacqueline Tarsa LeBaron is wanted in connection with four 1988 murders in Houston and Irving, Texas, according to a wanted poster on the agency's Web site. She's been a fugitive since 1992.
A telephone message left by The Associated Press with the Houston FBI office was not returned Saturday.
LeBaron is a daughter of Ervil LeBaron, the former leader of the Church of the Lamb of God, a polygamist sect with enclaves in Mexico.
The elder LeBaron ordered the executions of rival polygamists in the 1970s, investigators have said. In 1972 he was convicted in Utah of ordering family members to kill his brother, who was said to have disobeyed church laws.
Ervil LeBaron died in the Utah state prison in 1981. Before his death, he reportedly wrote a "bible" which included a commandment to kill disobedient church members.
It was also rumored that he left behind a "hit list" and that some of his 54 children were carrying out his commands.
Jacqueline LeBaron is one of six LeBaron family members charged with the June 1988 murders of three men who chose to leave the sect and the 8-year-old daughter of one victim. Each was shot in the head with a shotgun.
In 1995, three of the accused killers were convicted and sentenced to life in prison. Another was convicted of ordering the deaths and was sentenced to 45 years in prison. The youngest, who was 16 at the time of the murders, pleaded guilty to killing the child and served five years in prison.
Houston FBI special agent Todd Burns said there is renewed interest in Jacqueline LeBaron because a half brother who claims to have had a religious conversion in prison came forward with new information.
"He said they had an agreement to meet in Mexico. At one time they talked about meeting there before they got arrested and that never took place," Burns said. "He claims to not know anything about her whereabouts or whether she's living."
Authorities believe Jacqueline LeBaron, who has worked as an English teacher, is in Mexico, where she was born and where the family had several polygamist colonies.