Two Utahns were killed in separate accidents in Salt Lake County and Burley, Idaho, authorities say.

Killed:Stephanie Thomas, 18, Sandy

Donald Annis, 37, 2880 W. 54th South

Thomas was killed Thursday when the car she was in went off I-84, just south of the Cottrell port of entry.

Officer Fred Rice of the Idaho State Police said the driver, Julie Hayward, 17, Sandy, apparently fell asleep at the wheel. The car left the roadway, went into the median and rolled, he said.

Hayward was listed in serious condition at LDS Hospital in Salt Lake City Friday morning.

Annis died at Cottonwood Hospital from injuries suffered in a car-semitrailer truck collision on I-215 at about 500 West, the Utah Highway Patrol said.

Annis' car crashed into the rear of a semitrailer truck stopped in I-215 traffic lanes 215 because of another accident, the highway patrol said. Trooper Jim Bourdon said Annis was headed east Thursday when his compact car hit the rear of the gravel truck at about 55 to 50 miles per hour.

"Why (Annis) didn't dodge the truck like everyone else is a mystery to me," Bourdon said. He speculated the sun may have been in Annis' eyes.

The truck driver, Weldon Clapper, 53, Murray, also was taken to the hospital for treatment following the 7:15 a.m. Thursday accident.