A truck driver has been charged with death by auto after crashing into a limousine carrying US comedian Tracy Morgan and several of his friends.

It's believed the driver, 35-year-old Kevin Roper, of Jonesboro, Georgia, was asleep at the wheel.

According to New Jersey State Police Sgt. Gregory Williams, the driver "failed to observe slow-moving traffic ahead. He observed at the last minute - just prior to impact- the limo bus carrying Morgan and his party."

Middlesex County prosecutors said Roper faces four counts of "assault by auto" stemming from the crash. His bail was set at $50,000.

Morgan is in a critical condition after the limousine he was travelling in overturned in a six car pile up.

The 45-year-old 30 Rock star was travelling with six people in the vehicle when it was involved in a collision at the New Jersey Turnpike at 1am on Saturday morning. (7 June)

Two tractor-trailers, a SUV and two cars were reportedly involved in the crash. Alcohol is not believed to have been a factor in the crash.

Morgan is in intensive care at the Robert Wood Johnson University Hospital Centre in New Brunswick, New Jersey.

Spokesman Lewis Kay said in a statement that the actor's condition remains unchanged.

"His family is now with him and he is receiving excellent care," "We don't anticipate much of a change in his condition today but will provide a further update once more information becomes available."

One of the passengers travelling with the New York-based actor was killed in the accident. Seven others were taken to hospital, four of whom are in critical condition.

Sergeant Gregory Williams told CNN: "The limo bus overturned at the New Jersey Turnpike: "Looks like one of the tractor-trailers may have rear-ended that limo bus, but that's preliminary at this time."

Morgan, who starred in Saturday Night Live for seven years, had been performing in his show called Tracy Morgan - Turn It Funny! at Delaware's Dover Downs Hotel and Casino on Friday night.

He was due to perform in North Carolina tonight, but the show has been cancelled.

Fans and friends of the star have turned to Twitter to offer good wishes and prayers for his recovery.

Rapper Puff Diddy posted a tweet saying: "Sending prayers to Tracy Morgan and all involved in the accident!! We never know what can happen at anytime!"

Tracy Morgan first came to fame on the sketch-comedy show Saturday Night Live! in 1996. This was followed by the successful self-titled shows Morgan and The Tracy Morgan Show.

The comedian went on to join the hit NBC show 30 Rock in which he plays a caricature of himself.

Last July, Morgan celebrated the birth of his baby girl, Maven, with fiancée Megan Wollover. The actor also has three adult sons from a previous marriage.