ELLABELLE, Ga. (AP) â" Five people died early Wednesday in a chain-reaction crash on Interstate 16 west of Savannah that authorities said began when a tractor-trailer failed to slow down and smashed into stop-and-go traffic.

Those killed were traveling in two passenger vehicles mangled by the crash. The tractor-trailer plowed into an SUV, then rolled over a small passenger car that burst into flames, said Sgt. 1st Class Chris Nease of the Georgia State Patrol. The big truck came to a halt after slamming into the back of a tanker.

A total of seven vehicles ended up damaged in the collision and three additional people were injured.

The deadly crash happened at about 6 a.m. on the highway that connects Macon and Savannah. Despite the early hour, Nease said, traffic was heavy because an unrelated wreck about a mile ahead was forcing motorists move at a slow pace.

"Traffic was sort of stop-and-go when the tractor-trailer came along and struck one of the passenger vehicles in the rear," Nease said. "We're still trying to piece it all together. It's a terrible day."

Some motorists were stuck at a standstill for more than six hours as road crews and tow trucks worked to clear the wreckage. Even after those vehicles were allowed to pass, troopers kept a 6-mile stretch of eastbound I-16 closed as they continued to investigate the crash scene in Bryan County, about 20 miles west of Savannah.

Nease said the driver of the tractor-trailer had not been cited as investigators worked to figure out exactly what happened. State troopers said weather conditions did not appear to be a factor.

"There was no fog or smoke. It was clear as a bell," said Sgt. Chris Rodewolt of the State Patrol. "We did have heavy, heavy traffic."

Two mangled passenger vehicles could be seen at the bottom of an embankment beside the interstate. In front of them, just off the highway, was a tractor-trailer with its cab smashed into the back of a tanker truck.

State troopers Wednesday afternoon were still working to identify some of the five people killed, Nease said. Authorities planned to withhold their names until all of the victims' families had been notified.