"At that time of night, there was ungodly high winds and so visibility probably wasn't great out there in the middle of the desert on a dirt road," said Mohave County Sheriff's Office Chief Deputy Jim McCabe.
Investigators are looking at speed and alcohol as possible factors in the crash and have scheduled autopsies for Monday.
Only 16-year-old Nakita Timpson, whose birthday the group apparently was celebrating, survived the crash and was flown to a Utah hospital.
Her brother, 19-year-old Jamison Timpson, was killed, as was their cousin who was driving, 22-year-old Carl Holm. All three grew up in the Fundamentalist Church of Jesus Christ of Latter-Day Saints before leaving or being forced out Nakita Timpson very recently, friends and relatives said.
The youngest victim, Virgel Roundy, 15, was also from the Warren Jeffs-led polygamous sect; his father is the town's police chief. Monica Bistline, 17, lived in the community until she was about 12, when she left with their mother. Her father stayed until just last week, when he left and began reconnecting with his family.
"She was telling me before she died how excited he was," said LeRae Barlow, 16. She lost two of her best friends in the crash: Bistline and 17-year-old Rachel Anne Colgrove, whose family wasn't part of the sect but lived in nearby Cane Beds, Ariz.
Colgrove, she said, loved the Arizona strip area where the crash happened, as did Holm.
"I think it was a way to get out, away from everything and leave your problems behind," she said. "That's the feeling you have when you're down there, that nothing else matters, there's no one around and you have fun."
Some of those problems may have been turmoil in their families and communities: In the past year, Jeffs has tightened the rules on his people to sweltering levels, even as some 1,000 members broke away to follow a rival prophet. A third community, Centennial Park, split more than 20 years ago and has little official communication with the Jeffs group.
"This tragic accident has clearly affected all walks of life in our community, regardless of where people live and what they believe," said former FLDS spokesman Willie Jessop. "The dynamics of the children involved has affected everyone."
Then there are residents who aren't polygamists, such as the Colgrove family.
Rachel Colgrove befriended several young people who had been kicked out of the sect, said her mother, Stefanie Colgrove.
"I admired that in her she extended a friendship to them, helped them feel love, that someone cared for them," Stefanie Colgrove said. "That's her personality."
Her daughter called about 10 p.m. Tuesday asking if Bistline could sleep over, and she told her to return home soon, Stefanie Colgrove said. She started to worry when they hadn't returned in 30 minutes, but her daughter didn't say where they were. Roundy's brother, she said, finally found the Suburban in a remote ditch when he went looking on an all-terrain vehicle after discovering the teen missing from his bed.
Not all the victims were killed on impact, she said. Nakita has told her family that she talked to some of the teens after the crash, but they died before help arrived.
At the El Capitan school in Colorado City where Bistline attended school along with Rachel Colgrove, teacher Craig Chatwin said students form strong bonds and both victims were well-known.
"We're a tight community. … This cuts pretty deep," said Chatwin. His mother, Charlette, also said the accident had spanned religious divides.
Utah, U.S. and Arizona flags were lowered to half-staff, and three counselors were at the 500-student school.
"We tried to carry on as normal as possible," said assistant principal Fawneta Carroll. "We are trying to work with teachers to talk to the [students]. We find it helps deal with the grief."
Carroll described both girls as "vivacious, fun and energetic."
Richard Holm, an uncle to the three cousins, said both families were torn apart when Warren Jeffs excommunicated men.
"It's one thing for a relationship to divorce," but the separation by a religious leader can be devastating to children, he said.
He rented a house to Jamison Timpson for several months, and other boys often came to spend time there away from FLDS prohibitions against watching television, he said.
"Most of the young boys just don't have any bright picture at all of the future," he said. "They're trying to leave and find happiness, yet have fond memories of home."
The Associated Press contributed to this story.
The Polygamy Blog: http://bit.ly/Ar3JVq
Monica Joy Bistline • 17, of Apple Valley
Carl Otto Nathaniel Holm • 22, of Hildale
Rachel Anne Colgrove • 17, of Cane Beds, Ariz.
Virgel Taylor Roundy • 15 of Colorado City, Ariz.
Jamison Holm Timpson • 19, of Colorado City, Ariz.
Nakita Timpson • 16, of Colorado City, Ariz.