A charter bus traveling on a Mojave Desert freeway flipped on its side Saturday morning, killing a woman and injuring 22 other people, authorities said.

The bus was the only vehicle involved in the wreck on Interstate 40, about 115 miles southwest of Las Vegas, said San Bernardino County Fire Department spokeswoman Tracey Martinez.

"It did not roll over but it did land on its side," she said.

Witnesses said the bus drifted across lanes and into the median, Officer Taj Johnson of the California Highway Patrol said.

Investigators were studying skid marks and hoped to talk to the driver to determine the cause of the crash, Johnson said.

A woman was thrown from the bus and died, Martinez said. Eight other people received severe injuries and 14 had minor to moderate injuries. The driver was among the injured, who were all adults.

Martinez said the bus had picked up its passengers in Culver City and was headed to the gambling town of Laughlin, Nev. It crashed about three miles east of the town of Ludlow shortly before 11 a.m.

The cause of the crash about was under investigation.

The bus is owned by Royal American Tours & Charter of Glendale. It was not immediately clear what group had chartered the bus, and a man who answered the phone at Royal American's office said he did not have any details about the trip or the crash.