A tour bus returning from a casino crashed into a freight truck on Sunday in Palm Springs, California, killing 13 people and injuring 31 others, according to state police.
The bus driver was among those killed, California Highway Patrol division Chief Jim Abele said at a press conference. The freight truck driver was injured.
Injuries range from minor to moderate, Abele said.
The 1996 MCI bus, operated by USA Holiday, was returning to Los Angeles from the Red Earth Casino in Thermal, California, according to Abele.
The accident happened at 5:17 a.m. local time on westbound Interstate 10, officials said. The cause was not immediately known.
The CHP and the National Transportation Safety Board are investigating.
It’s unknown whether drugs, alcohol or fatigue were factors in the accident, Abele said, but the speed of the bus was so significant that when the bus hit the back of the big rig, the trailer entered approximately 15 feet into the bus.
Survivors said most passengers were asleep at the time of the accident, Abele said. The victims were found in their seats.
The victims’ identities were largely unknown due to a “swift extraction” by first responders, but all of the passengers are believed to be adults, Abele said.
“In almost 35 years I’ve never been to a crash where there’s been 13 confirmed fatalities. So, It’s tough,” he said. “It’s tough for all of us.”
He said the bus had been inspected in 2014, 2015 and, most recently, in April of this year, with no mechanical problems reported.
Early videos from the scene show dozens of firefighters with ladders inside the mangled remains of the tour bus, struggling to reach the victims.
CNN affiliate KESQ reported that rescuers used a crane to search the wreckage.
The California Highway Patrol said the highway would be closed for several hours.
Sunday’s crash is among the deadliest in California in recent years.
Ten people were killed in April 2014 when a FedEx tractor-trailer crossed a median on Interstate 5 north of Sacramento and slammed into a bus carrying high school students from Los Angeles on their way to visit a college campus.