In the pre-dawn hours Sunday, dozens of passengers on a tour bus — most of them reportedly asleep as they made their way back to Los Angeles after an organized trip to a local casino — were jolted awake in the most horrific way.

Ahead of them on Interstate 10 was a semi-truck that officials would later estimate was driving about 5 mph.

The bus was moving at a much higher speed.

About 5:17 a.m., the bus collided with the truck with such force that the first third of the bus became enmeshed in the truck’s trailer.

“The speed of the bus was so significant that when it hit the back of the big-rig trailer, the trailer itself entered about 15 feet into the bus,” California Highway Patrol Border Division Chief Jim Abele told reporters at a news conference Sunday.

Thirteen people were killed in the crash and 31 injured people were taken to hospitals, officials said. All of them were adults, with injuries ranging from minor to critical.

“In almost 35 years, I’ve never been to a crash where there’s been 13 confirmed [fatalities],” Abele said. “So, it’s tough. It’s tough for all of us. … And you never get used to it.”

As of Monday morning, the Riverside County Coroner’s Office had not released names of the victims. Of the 13 killed, 10 were women and three were men.

The USA Holiday tour bus had been driving toward Los Angeles from the Red Earth Casino, about an hour’s drive southeast of where the crash took place, CHP spokesman Mike Radford said.

When CHP officers arrived, they found a gruesome scene that blocked much of the traffic on the I-10 in Desert Hot Springs, a small city about 10 miles north of Palm Springs, he said.

Photos of the crash showed a badly mangled tour bus, with its front end crushed into the back of the big rig’s trailer.

“The front six rows, where 12 people had been sitting, were squashed together. Everyone, dead and alive, was covered with blood,” bus passenger Miguel Martinez told the Los Angeles Times in a tearful interview after he was released from a hospital. “The right side of one man’s face was peeled back.”

“I was awakened by the sounds of people screaming for help,” another passenger, Ana Car, 61, told the Times. “I noticed a heavy-set woman lying in the center aisle to my right yelling, ‘My legs! My legs!’ ”

Traffic had been slowed on a stretch of I-10 for a maintenance crew, the Associated Press reported. A CHP official said the tour bus had been traveling faster than the truck, but a trauma surgeon said facial injuries to passengers suggested that the bus was slowing down before the collision, according to the AP.

Emergency responders had to lift the trailer with tow trucks to pull the semi-truck forward, and firefighters propped ladders directly against the tour bus’s windows to be able to reach and remove victims, the Desert Sun reported.

The remains of the tour bus — including seats that had been strewn across the freeway — had been cleared by noon Sunday, the Los Angeles Times reported.

Coroner vans removed white body bags, two at a time, from the side of the road, according to the newspaper.

The driver of the bus was among those killed, Abele told reporters. The driver of the semi-truck, which had been hauling food products, had minor injuries, the CHP official said.

The majority of the bodies were in their seats, indicating that passengers were seated properly.

Abele told reporters Sunday that investigators would be checking to see whether the 1996 bus contained a “black box” type of data recorder that could give them clues as to why the crash happened. It was too soon to determine whether speed, alcohol, distraction or fatigue were factors, he said.

“Right now we’re looking at everything,” Abele said. “We may not determine how the accident occurred because the driver was killed.”

The tour bus was inspected in April and had no mechanical problems, Abele said.

The crash snarled traffic on I-10 for hours. Chris and Rachel Williams told the Desert Sun that they were about five vehicles east of the crash and remained stuck on the highway for more than an hour.

“We’re doing good. We’re just saying our prayers for the people involved in this situation,” Chris Williams told the paper. “This is a day that will be remembered.”

Late Sunday morning, the CHP issued a traffic alert for the Coachella Valley and noted that all westbound lanes of I-10 would be closed for some time.

“We have a major incident with a freeway closure on westbound I-10 west of Indian Canyon Road in Palm Springs,” the agency said in a statement. “A collision involving a semi-truck and a tour bus is under investigation, and all westbound lanes of I-10 are closed for an unknown duration. Detours are set up to exit at Indian Canyon and go to SR-62. Please drive safe.”

An Instagram account for USA Holiday showed that the California-based tour bus company advertised regular trips to Las Vegas and other casinos, picking up passengers from Los Angeles’s Koreatown and Panorama City neighborhoods.

A call to a number listed for the company was not returned Sunday. By Sunday afternoon, the Instagram account was no longer publicly visible.

The National Transportation Safety Board said Sunday that it was sending a team to investigate.

The crash occurred near Palm Springs, a city that already was grieving the recent loss of two police officers.

In early October, a man wearing body armor opened fire on Palm Springs officers — killing two and injuring a third — as they responded to a domestic-disturbance call in the city.

One of the officers killed, Lesley Zerebny, 27, was the mother of a 4-month-old child and had recently returned from maternity leave.

The other, Jose Gilbert “Gil” Vega, 63, had been scheduled to retire in December after more than three decades on the force. He had chosen to work overtime on the day of his death.

This post, originally published on Oct. 23, has been updated.

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