WILLIAMS – Authorities have begun investigating whether a bus driver who had a string of motor vehicle offenses and a history of substance abuse was under the influence of drugs or alcohol when his casino-bound bus crashed, killing eight people.

As victims flocked to hospitals in search of loved ones, the driver was arrested on suspicion of driving under the influence Monday, a day after his charter bus ran into a ditch.

Authorities said they were investigating the possibility that the driver may have been on prescription or nonprescription drugs. Blood test results are not expected for two to six weeks.

Sunday's accident was at least the eighth serious crash in the U.S. in the last three years involving buses carrying people to and from casinos.

Investigators said the bus had an invalid license plate, and they were also looking into whether the driver had proper permits to operate the vehicle. The bus ran off the road while taking passengers to a Northern California casino. About 30 people were injured.

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

Watts was arrested as he lay critically injured in his hospital bed. His condition had improved to fair, Woodland Memorial Hospital spokeswoman Lourdes Edralin said Tuesday. His mother said he had wrestled with drug and alcohol problems, was jailed several times on drug charges and had smashed a car carrying a friend into a tree a few years ago, though neither was seriously hurt.

He was a longtime truck driver, but had been unable to find a trucking job since being released from jail, said his mother Chaney Mae Watts.

In 1981 and then 1983, Watts served state prison time for receiving stolen property, and again in 1996, for check fraud and credit card theft. In 1998, he spent over a year in prison for possession of marijuana for sale and possession of a destructive device.

His latest state term was for possession of a firearm by an ex-felon. He was paroled in Dec. 2007 after almost six months in prison, according to the state Department of Corrections and Rehabilitation.

His mother said she believed the crash came on her son's first day behind the wheel of the bus after several training trips watching the owner drive. She and her husband told their son they were uncomfortable with him driving a vehicle that carried people instead of cargo.

“He wasn't the best driver,” she said. “He knew we didn't want him to drive.”

John Poyner, district attorney for Colusa County, said it will be at least two to three months before the full accident reports are in and any charges are filed.

The bus carrying the driver and 42 passengers, many Laotian, was heading to the Colusa Casino Resort. According to a witness, it drifted off a rural two-lane road before the driver “overcorrected” and swerved back. The bus ejected some passengers as it rolled and crushed others, said CHP spokesman, Patrick Landreth.

Families flooded hospitals looking for relatives who may have been involved in the crash.

Yvonne Haynes, 35, of Merced got a phone call Sunday night from her brother Tou Xiong, 29, saying there had been a bus accident. They started calling hospitals looking for their mother.

Finally, at 3 a.m., the siblings found their mother at UC Davis Medical Center in Sacramento. Mai Cha, 74, of Sacramento has a broken rib, face and right wrist and with the tubes in her mouth, she cannot speak, said Haynes. Cha and two other patients at the hospital were listed in serious condition; four others were listed in fair condition.

Their aunt also was an injured passenger, 67-year-old Ge Vue of Sacramento. Her son, Xou Xiong, 26, said his mother described the crash to him.

“All of a sudden the bus swerved and then it felt like the driver tried to come back to the road and that made it worse,” Xiong said. “She said as soon as she felt the impact, she flew to the back. That's all she remembered. She got up and tried to look for my aunt and saw her laying there with another lady on top of her.

“She was shaking her, pulling her hand. She was trying to talk to her and she wasn't responding,” Xiong said.

The CHP identified the dead as Daniel E. Cobb, 68, of Sacramento and Modesto, and Lou Her, 68; Muang Saephanh, 68; Khou Yang, 67; Meuay Saelee, 74; Fin Saechae, 64; and Ma Vang, 60, all of Sacramento. Family members also identified Xee Vang, 87, of Sacramento.

Three patients at Oroville Hospital were stable, and at least three patients treated at area hospitals were released Monday.

Authorities said they were investigating if Cobbs Bus Services owned the bus, but refused to say why they focused on that company. They also wouldn't say if Cobb, who died in the crash, was the owner of the company.

A man outside a home that is the primary listing for Cobb's business in Sacramento said the family was not ready to make a statement and declined further comment.

Associated Press writers Juliana Barbassa, Malia Wollan and Marcus Wohlsen in San Francisco and Samantha Young and Juliet Williams in Sacramento contributed to this report. AP researchers Monika Mathur and Jennifer Farrar also contributed.