At least 25 people were injured Thursday when a commuter bus crashed and burned while shuttling workers to a casino on the Nevada-California state line, authorities said.

No one died in the 2:15 p.m. wreck, which left the bus a charred metal skeleton alongside the southbound lanes of Interstate 15, about seven miles from the state line town of Primm.

"I don't know what all the injuries were, but thanks to people who witnessed the crash and stopped, and a quick emergency response, there are no fatalities," said Trooper Kevin Honea, spokesman for the Nevada Department of Public Safety.

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The full-sized tour bus was carrying about 30 employees to a casino in Primm when it ran off the side of the freeway, struck a metal guardrail and slid along a retaining wall for more than 600 feet, Honea said.

The bus's fuel tanks were breached in the crash before the bus reached the end of the retaining wall and tipped over in the desert next to the three-lane highway.

Honea said it appeared most people got out of the bus before fuel ignited and the bus was engulfed in flames.

Three critically injured people were flown by medical helicopter to University Medical Center in Las Vegas, and 22 others were taken in stable condition to five Las Vegas area hospitals, Clark County fire spokesman Scott Allison said.

The male bus driver was treated for second-degree burns to his legs, Allison said. He was not identified.

Honea said the driver faced questioning by investigators, who did not immediately know what caused the crash.

"It could have been a blown tire, it could have been mechanical error or driver error," the NHP trooper said. "We're not ruling out anything. It's real preliminary."

Las Vegas-based Herbst Gaming Inc. owns all three hotel-casinos in Primm, including Buffalo Bill's, Primm Valley and Whiskey Pete's. Company officials did not immediately respond to messages seeking comment.

California-bound traffic was backed up for several miles south of Las Vegas, with the NHP allowing vehicles to pass slowly on the paved median of the highway.

"It's going to be backed up down there for quite a while," Allison said.