The six-vehicle crash reported earlier today that left one dead and several, including comedian Tracy Morgan, in critical condition was caused when the driver of an 18-wheeler began falling asleep at the wheel.

The driver did not recognize the slow moving traffic ahead of him and failed to stop in time, crashing into the limo bus carrying Morgan and several others, police told ABC News.

The accident happened early this morning on the New Jersey Turnpike, and Morgan, as well as other passengers, were taken to the Robert Wood Johnson Hospital in New Brunswick, NJ, where they remain under treatment.

Among those accompanying the 30 Rock star on the bus included comedian James "Jimmy Mack" McNair, who died in the crash. Morgan's assistant Jeff Millea is also in critical condition, and fellow comedians Ardie Fuqua and Harris Stanton are also in the hospital, but their status is still unknown.

According to a statementfrom Tracy's publicist, his family is with him and his condition is not expected to change today.