PALM SPRINGS ( — The California Highway Patrol said the driver of a tour bus did not brake before it slammed into the back of a big rig near Palm Springs early Sunday, killing the bus driver and 12 passengers and injuring 31 others.

Four people remained in critical condition at the Desert Regional Medical Center in Palm Springs. One patient was in serious condition. Another was in fair condition. Nine others were treated and released. They were transported to three hospitals across the Coachella Valley.

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CHP Border Division Chief Jim Abele emphasized Monday that the cause of crash was still unknown.

National Transportation Safety Board investigators said they planned to spend five to seven days on scene and review security videos that may show what the driver was doing between the time the bus arrived at the casino from 11 to 11:30 p.m. and left at 4 a.m.

The crash was reported around 5:15 a.m. Sunday on the westbound 10 Freeway, just west of Indian Canyon Drive, according to California Highway Patrol officers.

Authorities confirmed the tour bus, which was carrying 42 passengers home from Red Earth Casino in Thermal, had no seat belts and said the truck was going about 5 mph amid maintenance work that slowed highway traffic.

The bus was going as fast as 65 mph before slamming into the trailer, investigators said. The impact was so violent, the bus ended up 15 feet inside the trailer.

The driver, Teodulo Vides, was targeted in past lawsuits over other freeway wrecks. The 59-year-old also owned the USA Holiday bus company, which specialized in trips from Los Angeles to the region’s casinos.

According to court records, Vides was not the driver in the other crashes for which he was sued.

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In a 2007 case, a USA Holiday bus collided with a Honda Civic, killing the car’s driver and two passengers. Family members sued the driver and Vides, but the case was dismissed.

KNX 1070’s Jon Baird reported some people said he played at local casinos and “didn’t sleep”.

Speaking in Spanish, former passenger Nury Lima also said Vides often nodded off and drifting onto other lanes while behind the wheel.

The Riverside County Coroner’s Office Monday released the identities of 11 of the 12 passengers killed:

Zoila Aguilera, 72, Los Angeles
Conception Corvera, 57, of Palmdale
Milagros Gonzales, 72, Los Angeles
Gustavo Green, 62, Los Angeles
Isabel Jimenez Hernandez, 66, Los Angeles
Ana Gomes de Magallon, 71, Los Angeles
Yolanda Mendoza, 69, of Los Angeles
Dora Galvez de Rodriguez, 69, Los Angeles
Rosa Ruiz, 53, Los Angeles
Elvia Sanchez, 52, Los Angeles
Aracely Tije, 63, of Los Angeles

CBS2/KCAL9’s Kristine Lazar was at a growing memorial for the victims.

The truck driver was not seriously injured.

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The bus company’s owner, Vides Teogeo Elias, was cited in a 2008 crackdown at LAX for violations on state regulations, according to California Public Utilities Commission records.