The leader of a polygamist breakaway Mormon sect who was on the FBI's Most Wanted List has been arrested and faces sexual misconduct charges for allegedly arranging marriages between underage girls and older men, authorities said Tuesday.

Warren Steed Jeffs, 50, was taken into custody after he and two other people were pulled over late Monday by a Nevada Highway Patrol trooper on Interstate 15 north of Las Vegas, FBI spokesman David Staretz said.

The leader of the Fundamentalist Church of Jesus Christ of Latter-day Saints was wanted in Utah and Arizona on suspicion of sexual misconduct for allegedly arranging the marriages.

He assumed leadership of the sect in 2002 after the death of his 98-year-old father, Rulon Jeffs, who had 65 children by several women.

Jeffs took nearly all his father's widows as his own wives. He is said to have at least 40 wives and about 60 children.

Since May, Jeffs has been on the FBI's 10 Most Wanted list, with a $100,000 reward offered for information leading to his capture.

People linked to Jeffs have living quarters in a secretive compound near Pringle.

Bob Perry, supervisory senior resident agent of the Rapid City FBI office, said local law-enforcement officials remained watchful of the living quarters while Jeffs was on the loose.

However, he said, officials couldn't act until the residents of the house did something wrong, which never happened.

"We don't investigate people if we don't have any indication of any wrongdoing," Perry said.

Neighbors of the Pringle compound told the Journal in March that the noise of heavy equipment and semitrailers could be heard coming from the compound at all hours of the night.

But Perry said that no official complaints have been filed by neighbors.

"Somebody would have to tell us they're doing something wrong first," he said. "Just the basic information that things have gone wrong in that organization doesn't mean that they're occurring here."

However, he discussed the possiblity of some wrongdoing in Pringle while Jeffs faces other charges.

"I don't know if there is anything criminal going on down there, but I guess there's always the potential he could identify something," he said.

He said officials from Arizona had asked his department to watch the compound, something that will no longer be necessary.

Perry said the capture was welcome news.

"Well, we're always relieved when somebody comes off the top 10 list," he said.

Custer County Sheriff Rick Wheeler said he is "kind of relieved they got him captured," although he said the state Department of Criminal Investigations has been doing most of the investigation.

The arrest brings a few questions to mind, Wheeler said.

"I guess I wonder what's going to happen next," he said. "Who's going to take over the compounds or how things are going to change - or if they're going to change."

He said he still might visit the compound in Pringle.

"I might make a run out there anyway just to see what they say," he said.

The other two people in Jeffs' vehicle when he was arrested were identified as one of Warren Jeffs' wives, Naomi Jeffs, and a brother, Isaac Steed Jeffs, both 32, Staretz said. They were being interviewed by the FBI in Las Vegas but were not arrested.

Isaac Jeffs was driving a red Cadillac Escalade that was stopped for having no visible registration, Nevada state trooper Kevin Honea said. An FBI agent was summoned to confirm Jeffs' identity, Honea said.

Warren Jeffs is in federal custody in Las Vegas awaiting a court hearing on a federal charge of unlawful flight to avoid prosecution, Staretz said.

Arizona Attorney General Terry Goddard told KTAR-AM of Phoenix that Jeffs' arrest is "the beginning of the end of ... the tyrannical rule of a small group of people over the practically 10,000 followers of the FLDS sect." He predicted that it will inspire more people to come forward with allegations of sexual abuse.

Most of the church's members live in Hildale, Utah, and nearby Colorado City, Ariz.

Jeffs was indicted in June 2005 on an Arizona charge of arranging a marriage between a 16-year-old girl and a married man, and unlawful flight to avoid prosecution. He is charged in Utah with two felony counts of rape as an accomplice, for allegedly arranging the marriage of a teenage girl to an older man in Nevada.

The FLDS Church split from the Church of Jesus Christ of Latter-day Saints when the mainstream Mormon Church disavowed plural marriage more than 100 years ago.

Jeffs has been called a religious zealot and dangerous extremist by those familiar with his church.

During his four-year rule, the number of underage marriages - some involving girls as young as 13 - escalated into the hundreds, church dissidents said. They said that although the sect has long practiced the custom of arranged marriages, young girls were rarely married until Warren Jeffs came to power.

People expelled from the community said young men were sent away to avoid competition for brides. Older men were cast out for alleged disobedience, and their wives and children were reassigned by Jeffs to new husbands and fathers, the former members said.

"If this will bring an end to that, that will be a good thing," Ward Jeffs, an older half brother of Warren, said. "We're excited for the people down there, but we're very concerned about who might step up and take the leadership role."

It remained unclear Tuesday what would happen to the leadership of the church while Jeffs was incarcerated.

Federal and state law enforcement agencies will determine whether Jeffs should be extradited first to Utah or Arizona, said Steve Sorenson, a federal prosecutor in Salt Lake City. Utah's charges are more serious, and the federal unlawful flight charge was for leaving Utah, which could influence the decision, Sorenson said.