The driver of a Canadian travel company bus that crashed and killed 9 passengers in Oregon last month had slept for more than seven hours the night prior to the accident, a company attorney said Wednesday.

Attorney Mark Scheer’s comments come a day after the U.S. Department of Transportation revoked Vancouver, British Columbia-based Mi Joo Tour &Travel’s authority to provide passenger service in the United States after determining a driver was not properly rested when his bus crashed.

A Federal Motor Carrier Safety Administration investigation found that driver Haeng Kyu Hwang had been on duty for 92 hours in the eight-day stretch before the tragedy, exceeding the 70-hour federal limit.

“I can specifically say that he had seven and a half hours of sleep when they left the morning of the accident,” Scheer said.

Scheer didn’t address the federal report on Wednesday beyond saying the company had “concerns about the accuracy” of it. The attorney added that black ice was a “significant” factor in the bus losing control on an Oregon highway and bursting through a railing. Scheer said the bus had already made a stop the morning of the crash.

Thirty-eight people were injured. Most of the passengers in the bus heading to Boise, Idaho, were Korean.

Scheer said the driver was seriously injured in the crash, but has been cooperating with investigators. The driver is back in Vancouver.

“Mr. Hwang is a licensed driver. Mr. Hwang had previously worked as a school bus driver and truck driver with no accidents,” Scheer said. “He was in good health and he doesn’t use alcohol or tobacco.”

Scheer said Mi Joo Tour &Travel has no history of passenger injuries and continues to cooperate with authorities and has set up a helpline for passengers and their family members, including interpretation help.

The Oregon State Police and National Transportation Safety Board have yet to say what caused the Dec. 30 crash on Interstate 84 east of Pendleton.

The crash, Oregon’s deadliest since 1971, occurred near a spot called Deadman Pass, at the top of a steep, seven-mile descent from the Blue Mountains. A truck had applied sand to the icy road a few hours before the crash and was behind the bus making another run when the vehicle driven by Hwang plowed through a guardrail and 200 feet down an embankment.

On Tuesday, federal authorities also said the company’s authority to operate had been suspended for two months early last year because the firm didn’t pay a fine for failing to meet U.S. requirements for drug and alcohol testing.