WILLIAMS (AP) – The driver of a casino-bound charter bus that crashed and killed eight people is in critical condition and faces felony charges of driving under the influence, the California Highway Patrol said Oct. 6.

Quintin Watts, 52, of Stockton was arrested on suspicion of driving under the influence. Authorities were investigating whether prescription or nonprescription drugs, or alcohol, were involved in the Oct. 6 crash. They said it could be a combination.

Results of a blood test were not immediately released.

“We believe he was driving under the influence of something, that’s why we placed him under arrest,” patrol spokesman Robert Kays said Oct. 6.

The bus, which had an invalid license plate, drifted off a rural two-lane road before the driver “overcorrected” and swerved back, patrol spokesman Patrick Landreth said. The bus tumbled into a ditch, ejecting some passengers as it rolled and crushing others, police said.

“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,” Landreth said. “It was facing the opposite direction and it was on its wheels.”

The accident was at least the eighth in the last three years involving buses carrying people to and from casinos that caused deaths.