A National Transportation Safety Board investigator said a tour bus driver was distracted by a problem with his door just before the bus crashed near Hoover Dam last month.

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Peter Kotowski told reporters Saturday that investigators have not found anything wrong with the driver-side door nor have they found any other mechanical problems on the bus.

Witnesses said that door was briefly open before the driver lost control and the bus crashed Jan. 30, killing a tour guide and six Chinese tourists. The driver was among those injured and the NTSB wasn't able to interview him until recently.

Kotowski said the driver, 48-year-old Han Dong of Rosemead, Calif., was properly licensed.