JEAN, Nev. -- Those people injured in a shuttle bus crash near Primm are being treated at Las Vegas hospitals.

According to medical officials, University Medical Center has received seven people -- three via helicopter and four by ground, whose condition is unknown at this time. One of the critical patients is the male driver of the shuttle bus. He was treated for second-degree burns to his legs.

Sunrise Hospital has received six victims, who are all in good condition. Most of them are expected to be released Thursday night. Four people, listed in fair condition, have made it to St. Rose Sienna Hospital, while two more in good condition are at St. Rose San Martin Hospital. Five more people have arrived at Spring Valley hospital with unknown -- but not critical -- conditions.

The bus crashed on southbound Interstate 15 near Jean at about 2:15 p.m. Thursday, injuring at least 25 people, according to the Nevada Highway Patrol.

Officers said the commuter bus drifted off the right side of the road for an unknown reason. It then broke through a metal retainer and onto the outside of a cement median wall, police said. It continued driving against the wall until the wall's end, where -- police said -- it fell on its side. During the grinding, officers said the gas tank was ruptured, causing the bus to burst into flames.

The NHP said the full-sized bus was carrying about 30 employees to a casino in Primm, where Las Vegas-based Herbst Gaming Inc. owns all three properties.

There has been no comment yet from the company.

"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.

Everyone on board was trapped inside. Troopers said some good Samaritans pulled over, stepped in and started saving lives.

Investigators aren't sure yet why the bus ran off the three-lane freeway.

The scene has been cleared, and all travel lanes have been opened.