"They were all in one area and she just drove right through them," said Highway Patrol Sgt. Steve Cabrales.
The 20-year-old driver was jailed for investigation of driving under the influence involving controlled substances and felony reckless driving.
"We don't know whether she fell asleep or just what happened," Cabrales said.
The six were among 45 youths, ages 14 through 17, who had been sentenced to pick up trash along Interstate 15 for the Clark County Youth Services Department.
They were struck Sunday afternoon near the Las Vegas Motor Speedway, just north of the downtown area, Cabrales said.
"They had no warning at all. The van came off (the road) unexpectedly and just wiped them out," said Kirby Burgess, director of the county youth program.
Highway Patrol trooper Shane David estimated the van was traveling 75 mph, the legal speed limit. He said there was no evidence the van's brakes were applied before it hit the teen-agers.
The driver, identified as Jessica Williams, also was cited for investigation of drug possession and drug paraphernalia possession. David said she carried a California driver's license but is from Littlefield, Ariz.
She and her passengers were treated for minor injuries.
The victim's names and ages were not released.
The injured member of the work crew was in critical condition at University Medical Center.
By Robert Macy
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