FLORENCE, S.C. (AP) - Cars burst into flames in a five-vehicle crash in South Carolina that killed five people including an infant and snarled interstate traffic for hours, authorities and witnesses said.

The crash involving two commercial trucks happened Saturday night around 7:30 p.m. in the northbound lanes of Interstate 95 in Florence County, said State Highway Patrol Cpl. Sonny Collins. The northbound lanes were closed for hours afterward.

Among those killed were two parents and their child from Ontario, Canada, who were traveling in a Honda sedan. Florence County Coroner Keith von Lutcken identified them as Jeremiah Cross, 34; Crystal Cross, 32; and Grayson Cross, 7 months.

The coroner said the two people killed in a 2011 Jeep Cherokee were Jacqueline Ann McCann, 51, of Johnstown, Pa.; and 52-year-old Barry Himes, also from Pennsylvania. Himes' hometown wasn't provided.

Collins said he's not aware of injuries beyond those who were killed.

Media photos from the scene show two tractor-trailers and twisted and burned wreckage of other vehicles.

The Morning News of Florence reported that one mostly burned car was pinned under a tractor-trailer, and nearby another car was "fully burned." It said the second tractor-trailer was damaged.

Collins said he couldn't provide further details on what led to the crash and that it could be days before investigators release a cause.

Witness Vahid Hamzehnava told the Morning News he was a few cars back when he saw the accident happen.

"I tried to slow down with the flow of traffic and all of a sudden it just happened," Hamzehnava said. "When I got here I saw the truck driver get out ... and he thought the truck was going to explode, so he ran down the highway."

Hamzehnava said he and another witness ran toward the wreckage to try helping passengers but weren't able.

"We tried," he said. "There was nothing him and I could do."