A commuter van collided head-on with a tractor-trailer early Friday on a Mississippi River bridge, killing four people and injuring four others, authorities said.

Diesel fuel spilled from the 18-wheeler and caught fire near the Illinois end of the bridge. It was extinguished a short time later.

The four people killed were among seven in the van, which was headed westbound on the Martin Luther King Bridge (search) when the crash happened about 5:45 a.m., said Illinois State Police Master Sgt. Roger Hayes.

"The van crossed the center line and hit the truck head-on," Hayes said.

Authorities said the busy bridge, one of three that connect East St. Louis with the city of St. Louis on the Missouri side, would be closed most of the morning.

The van was operated by Illinois' Madison County Transit (search) as part of its RideFinders (search) program, which provides vans to groups of commuters for a monthly fee. Participating groups must have at least seven people, but the vans can accommodate 15 passengers.

Names of those killed were being withheld while their families were notified. It was not immediately clear where the injured truck driver and the three injured commuters were taken.

The bridge has two lanes in each direction, separated by a double yellow line.

Traffic halted on the bridge while authorities worked to investigate and clear the crash site. Smaller vehicles were led off the bridge but several larger vehicles, including trucks, remained in place, lacking space to turn around.