Las Vegas ? A tour bus driver had tried to fix a problem door and was blinded by the sun’s glare just before the bus crashed near Hoover Dam last month, killing seven passengers, an investigator said Saturday.

“We know he was distracted by that door,” National Transportation Safety Board lead investigator Peter Kotowski told reporters. Witnesses told investigators the driver’s side door was open at one point just before the bus crashed.

A tour guide and six Chinese tourists were killed in the crash along U.S. 93 in Arizona, 26 miles south of the Nevada state line. Ten others were injured, including the driver. Han Dong, 48, of Rosemead, Calif., remained hospitalized in fair condition Saturday.