LUDLOW -- A charter bus overturned Saturday on a Mojave Desert freeway, killing a woman and injuring 22 other people, authorities said.

The bus was heading to the gambling town of Laughlin, Nev., when it crashed about three miles east of the town of Ludlow shortly before 11 a.m., said Tracey Martinez, a spokeswoman for the San Bernardino County Fire Department.

"There were no other vehicles involved," she said. "It did not roll over but it did land on its side."

A woman was flung from the bus and died, she said. Eight other people received severe injuries and 14 had minor to moderate injuries.

The driver was among the injured, who were all adults.

The bus had picked up its passengers at the Fox Hills Mall in Culver City.

The crash happened on Interstate 40, about two hours from Las Vegas. Helicopters and ambulances were called to take the injured to hospitals, and the interstate's eastbound lanes were closed for a time. All lanes were reopened Saturday evening.

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

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

The bus is owned by Royal American Tours & Charter of Glendale.

According to the company's Web site, Royal American was founded in 2002 and provides transportation for "event planners, tour operators, employers, casino trips, hospitals, universities, park districts, senior centers, private groups and also individuals."

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.

"We have no clue of what's going on either," said the man, who declined to give his name.

The names of the victims were not released Saturday pending notification of family, Johnson said.