NEW YORK - New York State Police and National Transportation Safety Board investigators spent more than three-and-a-half hours on Tuesday, March 15, questioning the New York tour bus driver involved in a weekend collision that killed 15 people and injured 19 others, according to NBC New York.

The March 12 fatal crash has placed a national spotlight on the issue of commercial driver screening and background check processes. Media reports have revealed the driver has a criminal record that includes a 2003 arrest for driving with a suspended license and possessing three police radio scanners.

State and federal investigators questioned bus driver Ophadell Williams at the Brooklyn headquarters of World Wide Tours, his employer.

Williams was driving the bus back from a Connecticut casino to Manhattan's Chinatown when it skidded off the road and rammed into a highway sign post on I-95 in the Bronx at 5:30 a.m. on March 12.

Williams has not been charged with any crime connected to the crash, but the investigation is in its early stages, officials told NBC.

The New York State Inspector General is investigating how Williams obtained and retained a commercial driver's license, despite his criminal and driving records. According to NBC, Williams' criminal record also includes three felonies and two misdemeanors as an adult, including a guilty plea to a manslaughter charge. In addition, there were arrests for grand larceny and criminal possession of stolen property in 1998.

NBC reported that state and federal investigators are looking into the possibility that Williams fell asleep at the wheel or was distracted. A blood-alcohol breath test indicated he hadn't been drinking.

Passengers said the bus was drifting in and out of lanes just before the collision.