WILLIAMS, CA --- A bus driver with a history of motor vehicle offenses and substance abuse was arrested on suspicion of driving under the influence Monday, Oct. 6, after his charter bus ran into a ditch, killing eight people.

The Associated Press reported that investigators said the bus had an invalid license plate, and they were trying to discover whether the driver had proper permits to operate the bus, which was bound for a gambling hall in northern California. About 30 people were injured in the collision.

Records show 52-year-old Quintin Watts had previously been cited for speeding and other violations, resulting in loss of his license for nearly two years. He regained his driving privileges last January, AP reported.

Watts was arrested as he lay critically injured in a hospital bed. His mother told AP he has long struggled with drug and alcohol problems, has served jail time on drug charges, and had smashed a car carrying a friend into a tree a few years ago, though neither was seriously injured.

Watts was a longtime truck driver, but struggled to find a trucking job since being released from jail on a domestic violence charge six months ago, his mother told AP.

The accident was at least the eighth serious crash in the U.S. in the past three years involving buses taking people to and from casinos, AP reported. Authorities were investigating whether prescription or nonprescription drugs or alcohol, or a combination of both, were involved in the crash. Blood test results will become available in two to six weeks.

"We believe he was driving under the influence of something. That's why we placed him under arrest," California Highway Patrol spokesman Robert Kays told AP.

The bus carrying about 43 passengers, many Laotian, was heading to the Colusa Casino Resort. The bus reportedly drifted off a rural two-lane road before the driver "overcorrected" and swerved back. "The roof was collapsed down, the windows were broken out, and the bus was not only rolled over onto its side, it rolled completely over," CHP sokesman Patrick Landreth told AP. "It was facing the opposite direction and it was on its wheels."