About a dozen freight cars caught fire after a CN train derailed northwest of Chicago. (Scott Morgan/Rockford Register-Star/Associated Press)A woman was killed in a fiery crash Friday when a CN freight train carrying a load of ethanol derailed and plowed into her stopped car northwest of Chicago, forcing the evacuation of hundreds of homes.

The massive fire that ensued burned out of control for several hours. Fire officials in Rockford, Ill., said the blaze was too hot to get near and it was best to let the inferno peter out by itself.

According to the Rockford Register-Star newspaper, the Chicago-bound train began hydroplaning in standing water as it approached a street crossing and some rail cars left the tracks moments before exploding.

The woman killed was in a vehicle that was stopped and waiting for the train to pass. Three other occupants were able to run from the car as it was bombarded with flying railroad ties. They were severely burned by flaming ethanol and were hospitalized in serious to critical condition, Rockford Fire Chief Derek Bergsten said.

Two crewmen on the eastbound train escaped injury, CN Rail spokesman Patrick Waldron said. The crew were able to pull 64 cars away from the scene. The train was hauling 114 cars, 74 of which contained highly flammable ethanol, also known as ethyl alcohol.

About a dozen of the cars were burning, Bergsten said.

"At first I thought it was a tornado because they always say a tornado sounds like a train coming," said Jeff Tilley, a Register-Star employee who lives near the scene of the derailment.

Officials evacuated the area on the edge of Rockford, about 130 kilometres northwest of Chicago, Friday night amid concerns about air pollution and the chance that more of the train's cars might catch fire.

Kirk Wilson, a fire chief in nearby Rockton, said he expected the ethanol to continue burning until later Saturday.

"We're letting the product burn itself out," he said. "We can't get too close to it. We're observing everything through binoculars from about 200 or 300 feet [60 to 90 metres] away.

"The situation is not under control, but we are making progress in getting it under control," added Wilson, whose department was one of at least 26 that responded to the scene of the derailment. "It's very dangerous. It's very explosive. We're not risking any firefighters' lives."

Parts of northern Illinois received up to 10 centimetres of rain Friday, and Chicago's O'Hare International Airport, east of Rockford, recorded a record nine centimetres.

The derailment was being investigated by Canadian National and the U.S. Federal Railroad Administration. Members of the U.S. National Transportation Safety Board were en route to the accident early Saturday.

With files from The Associated Press