NEW BRUNSWICK, N.J. – Accident investigators are looking into what role a truck driver’s interstate commute played in the fatal New Jersey crash that also injured comedian Tracy Morgan.

Wal-Mart driver Kevin Roper, who pleaded not guilty to death by auto and assault by auto charges on Wednesday, lived in Georgia, but his job was based in Delaware, said National Transportation Safety Board spokeswoman Kelly Nantel.

A criminal complaint alleges that the 35-year-old Roper hadn’t slept for more than 24 hours before the accident when he allegedly swerved to avoid slowed traffic and hit Morgan’s limo early Saturday.

Wal-Mart has not explained what Roper’s driving route was. The company has said it believes he was in compliance with federal safety regulations.

Roper’s bail was kept at $50,000. Roper and his attorney, David Glassman, refused to answer reporters’ questions after the hearing about whether Roper was the author of tweets from a Twitter account bearing his name and featuring his picture and calling reports of his not having slept for 24 hours before the accident “complete BS!”

A conviction on a death by auto charge carries a five-to-10-year prison sentence. Each assault by auto charge is punishable by up to 18 months in prison.

The 45-year-old Morgan suffered a broken femur, a broken nose and several broken ribs. His friend and fellow comedian James McNair was killed, and two other passengers were seriously injured.

Morgan underwent surgery for his broken leg and remained in critical but stable condition.

Accidents involving tired truckers tend to have larger numbers of deaths and severe injuries because of the damage inflicted by trucks weighing tens of thousands of pounds, according to safety investigators.

Scientists say sleep deprivation affects behaviour much like alcohol, eroding judgment and slowing reflexes. In several accidents investigated by the NTSB, commercial drivers suffering from lack of sleep have driven straight into vehicles clearly visible to them without applying brakes or applying them too late because they failed to grasp what they were seeing.

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Associated Press writer Joan Lowy reported from Washington.