(Recasts lead, adds Morgan TV show update)
By Victoria Cavaliere
NEW YORK, June 10 (Reuters) - A witness to a collision on a New Jersey highway that critically injured comedian Tracy Morgan and killed one of his associates described it as a "terrible accident" in a 911 call, according to audio recordings released on Tuesday.
"The car flipped. It's on its side," the unidentified woman also told an emergency operator moments after the crash early on Saturday in which a Wal-Mart tractor trailer slammed into a limousine van carrying Morgan and several other people.
"There was an accident on the New Jersey Turnpike. It happened behind us," another caller said in 911 recordings released by the New Jersey State Police.
Morgan, 45, best known for his roles on "30 Rock" and "Saturday Night Live," and two other people riding in the van remained in a critical-care unit on Tuesday, said a spokeswoman at the Robert Wood Johnson University Hospital Center in New Brunswick, New Jersey.
Comic James "Jimmy Mack" McNair, 62, a writing partner of Morgan who was also in the van, died at the scene.
A fifth passenger was lightly hurt and released from the hospital.
Morgan's injuries included a broken leg, nose and ribs. He underwent surgery over the weekend, his spokesman Lewis Kay said in a statement Monday.
Kay dismissed online rumors that Morgan's leg had to be amputated. "Rumors about amputating his leg are completely fabricated," the statement said.
Morgan was scheduled to start shooting 10 episodes of a new half-hour comedy show in August, the Untitled Tracy Morgan Project, for Twenty-First Century Fox's cable network FX. The show was slated to air in January 2015 on FXX channel, the sister channel of FX.
"The only thing we are concerned with is the health and recovery of Tracy Morgan and the victims of this tragic accident. We will support Tracy and his family in every way possible throughout his recovery," the network said statement on Tuesday.
"At the point when Tracy has recovered and decides that he is ready to go back to work, his show will be waiting for him."
The driver of the Wal-Mart truck, Kevin Roper, 35, has been charged with vehicular homicide and injury by auto for operating his commercial vehicle after not having slept for more than 24 hours, resulting in the fatal crash, according to prosecutors.
He is due to appear in Middlesex County Superior Court on Wednesday.
Wal-Mart Stores Inc said on Tuesday that its 7,175 drivers meet some of the highest safety standards in the industry.
So-called drowsy driving, or driving with too little sleep, causes more than 100,000 crashes a year, resulting in 40,000 injuries and 1,550 deaths, according to the U.S. National Highway Traffic Safety Administration.
(Reporting by Victoria Cavaliere, additional reporting by Piya Sinha-Roy; Editing by Eric Beech, Gunna Dickson and Leslie Adler)