Tom Carver reports: "This is America's worst crash for six years"

Several carriages derailed and burst into flames after the train smashed into the tractor-trailer, which was carrying a heavy load of steel.

More than 200 passengers were on the train. A fire officer at the scene said most of the victims were in a sleeping car near the front, behind two baggage cars.

At least four people are still unaccounted for, but investigators say it is now unlikely that any survivors will be found.

At least four people are still unaccounted for

The train smashed into the trailer at about 21.40 local time at a railway crossing outside the town of Bourbonnais about 50 miles south of Chicago.

The train's two lead engines and six coaches were derailed, with the wreckage still burning for hours after the crash. The force of the impact caused the front engine to split in half.

Speeding offences

The train's black box, which should reveal its speed, is on its way to Chicago for examination.

Investigators are questioning how the tractor-trailer moved into the train's path despite crossing gates and lights that were apparently working.

Reports said the truck driver, John Stokes, 58, is understood to be driving on a probationary licence which he had obtained after passing a safety course following the speeding tickets.

Mr Stokes reportedly told investigators he did not see the train as he approached the tracks and that the lights started flashing after he started driving across.

Twisted metal

About 200 emergency workers have been working through twisted metal to rescue trapped passengers.

As each carriage was checked for possible survivors it was labelled 'empty' in large letters on the side.

"It's an unbelievable wreck," Lorri Girlak, a nearby resident told the local WMAQ-TV news station.

The train, known as City of New Orleans, runs between Chicago and New Orleans and was thought to be an hour into its journey when the accident happened.