The truck driver deemed responsible for a New Jersey traffic pile-up that put funnyman Tracy Morgan in the hospital and claimed the life of his comedian pal James 'jimmy Mack' Mcnair was speeding prior to the collision, according to U.S. transportation officials.

Kevin Roper, a driver for U.S. superstore Wal-Mart, stands accused of falling asleep behind the wheel of his vehicle after ploughing into the back of a limo bus carrying Morgan and his companions early on 7 June (14).

The impact of the collision killed MCNair and left Morgan and two others with serious injuries.

Roper pleaded not guilty to charges of vehicular homicide and assault by auto during a court hearing last week (11Jun14), but now a preliminary report released by officials from the National Transportation Safety Board (Ntsb) suggests the suspect had ignored speed limit signs to slow down on the New Jersey Turnpike due to construction.

Officials claim he had been driving at 65 miles (104 kilometres)-per-hour, instead of the advised 45 miles (72 kilometres)-per-hour moments before the crash. The regular speed limit on the highway is 55 miles (88 kilometres)-per-hour.

Prosecutors have also accused Roper of sleep deprivation, claiming he had been awake for more than 24 hours at the time of the fatal incident. He faces up to 10 years behind bars if authorities can prove he ignored sleep guidelines for a trucker.

Morgan remains hospitalised, but his condition has been upgraded from critical to fair.