Fatigue may be to blame for last year's deadly tour bus crash on I-95 in The Bronx.

According to federal investigators, documents show that during the three days prior to the accident, Ophadell Williams' cell phone and rental car were in almost continuous use when he claimed to have been sleeping.

Ophadell, a Brooklyn resident, has pleaded not guilty to multiple charges in connection with the crash. Fifteen people were killed when the bus overturned while returning from an overnight trip in Connecticut.