COLUMBUS, Ohio (Reuters) - A Norfolk Southern freight train derailed and burst into flames in Columbus, Ohio, early on Wednesday, forcing nearby residents to evacuate, authorities said.

The 98-car southbound train, with two locomotives, was carrying ethanol, and fire officials were letting the biofuel burn itself out, said Columbus Assistant Fire Chief Dave Whiting. He said 10 cars derailed and about three ruptured.

"It's contained, it's not spreading," Whiting said. "It's doing exactly what we want it to do. We haven't had to put anybody in harm's way."

About a hundred people were told to leave their homes within a one-mile radius of the derailment that took place near the state fairgrounds and Ohio State University, fire officials said.

The train, bound for North Carolina from Chicago, derailed at about 2 a.m. EDT, said Norfolk Southern spokesman Dave Pidgeon.

He said between 11 and 13 cars derailed but the exact number was undetermined. He also said two cars carrying ethanol were still burning hours after the derailment.

The cause was unknown and under investigation, Pidgeon said. The National Transportation Safety Board joined the investigation, he said.

Two people were injured and drove themselves to nearby hospitals, local media reported. Their conditions were unknown.

Johnnie Rouse, who lives down the street from the accident, said she was awakened by a loud boom.

"The sky was lit up like the sun had fallen or something," Rouse said.

"My daughter said 'Mama, Mama, get up, get up, get up, a train's exploding ... you've got to get out,'" she said.

Residents were likely to be able to return home later in the day after the fire burned out, which was expected to take a few hours, officials said.

Evacuee Kaila Thomas said there was a strong chemical smell in the air after the fire broke out. "We went to different places, and it smelled different each time," she said.

Other Norfolk Southern trains that were being held due to the derailment were expected to be moving soon through an alternate route, Pidgeon said.