WASHINGTON — Federal officials say a deadly New York tour bus crash last year was caused by a driver suffering from fatigue.

The National Transportation Safety Board, in a unanimous vote Tuesday, said the bus company, World Wide Tours of Greater New York, was also to blame for not providing adequate safety oversight of the driver, Ophadell Williams.

Federal regulators shut down the bus company for safety violations after the March 12, 2011, accident that claimed 15 lives. But the company's employees, buses and other assets were transferred to a closely related bus company that continues to operate, investigators said.

The bus was returning to New York's Chinatown from an overnight trip to a casino when it clattered along a highway guard rail, toppled over and crashed into the support pole for a highway sign.