NTSB continues on site safety investigation of deadly bus crash

ASHLAND, VA (WWBT) - The NTSB is closely examining Kin Yiu Cheung's driving history as well as the North Carolina-based tour bus company. Sky Express was almost shut down by the feds three days before Tuesday's deadly crash on Interstate 95.

The NTSB will resume its week-long on-site investigation Thursday morning. Investigators want to talk to the Sky Express bus driver and the company that put Cheung behind the wheel.

The NTSB "go team" is making significant progress said board member, Earl Weener. Cheung was the sole Sky Express worker on board the motor coach when it flipped onto its roof early Tuesday, killing four women and injuring 53. The NTSB recovered his driving logs.

"We have every intent to talk to the driver to interview him," said Weener.

While federal investigators examine the bus at an undisclosed location, state police ruled out mechanical malfunctions and has said driver fatigue is to blame.

"Fatigue we find to be an issue in basically all modes of transportation, but it's premature to say anything specific about this particular driver," said Weener.

Sky Express is also under the microscope. The U.S. Department of Transportation was about to shut down the company May 28.

Back on April 12, the Federal Motor Carrier Safety Administration gave the company a proposed unsatisfactory safety rating. It uncovered drug and alcohol and hours of service concerns. Nearly a month later on May 11, Sky Express filed an appeal, which was initially denied. But the FMCSA extended its review another ten days.

NTSB investigators traveled to North Carolina to speak with Sky Express executives.

"To understand more about this company, its process, its culture, and particularly its safety culture which we keep finding is becoming more and more an indicator of the quality of the operation," said Weener.

In ten days, the Office of Highway Safety will release a preliminary report on the crash.

Copyright 2011 WWBT NBC12. All rights reserved.