MOAB, Utah -- The Utah Highway Patrol and federal immigration officials were working Wednesday to identify the people involved in a crash that killed at least one of 16 people who were packed inside a minivan when it rolled on a state highway in southeastern Utah.

Patrol Sgt. Wade Breur said there was confusion as to how many people were killed in Tuesday's crash because a 20-year-old Guatemalan woman, who was dead at the scene, may have been identified twice in conflicting witness accounts. Breur said Wednesday afternoon there was only one fatality.

Initial reports from a Moab hospital administrator and a spokesman for the Mexican Consulate in Salt Lake City each had a second person dying in the crash.

Marla Shelby-Drabner, an administrator for Allen Memorial Hospital in Moab, told The Associated Press on Wednesday that she knew of only one fatality -- an unidentified person who was dead before arriving at the hospital -- but added that in the confusion after the accident Tuesday the victim may have been mistaken for a second individual.

Mexican Consulate spokesman Arturo Chavarria said Wednesday morning there was a second fatality, a female between the ages of 15 and 21, but was not available later in the day to try to clear up the discrepancy.

Breur said investigators were having a hard time establishing identities for several of the passengers, believed to be in the United States illegally, because some were using false names.

"Three guys were trying to claim the name of one guy," Breur said. "We're working with the immigration officials, trying to come up with something more accurate."

Two men who were in the van remained in critical condition Wednesday at St. Mary's Hospital in Grand Junction, Colo., Breur said.

Chavarria said the van was carrying seven Guatemalans and eight Mexican nationals.

Breur said one of the hospitalized men had papers indicating he was from India, but he was in critical condition and investigators were still trying to confirm his identity.

Breur said it appeared all of the people in the van were in the country illegally.

The driver, a 17-year-old boy, left the scene and was found walking along the road about one mile north of the crash site, Breur said. The teenager was turned over to immigration officials Wednesday.

The van, which was en route from Phoenix to Denver, drifted off the right side of the road on a curve, overcorrected and rolled several times, crossing both lanes of traffic before coming to rest in the sagebrush on the left side of the road, Lt. Todd Peterson said.

Investigators believe the driver may have fallen asleep or became drowsy.

"There were no skid marks on the roadway," Peterson said. "That leads us to believe the driver fell asleep."

The rollover on Utah 191 occurred about 315 miles southeast of Salt Lake City. The state road through remote country is commonly used to transport undocumented immigrants.

There is no evidence any of the passengers were wearing seatbelts, and three people were believed thrown from the vehicle when it rolled, the patrol said.

The Dodge minivan normally seats seven or eight, depending on how it is configured, but the middle seat had been taken out to make more room, but leaving only seats for five, Breur said.

"They were just crammed into this thing," he said.

On Monday, a passenger van carrying 12 people rolled over on Interstate 76 northwest of Denver, killing two people and injuring nine. Several of the people in the van were from Mexico, according to the Colorado State Patrol.