(Reuters) - A rail bridge collapsed on Friday over a creek in southern New Jersey, causing a Conrail freight train to derail and spill hazardous chemicals into the water, authorities said.

Five tanks of the freight train, which was carrying vinyl chloride, fell into the Mantua Creek, which feeds into the Delaware River near Philadelphia, the U.S. Coast Guard said.

Vinyl chloride, a highly toxic and flammable industrial chemical, was spilling from the tanks, said U.S. Coast Guard Petty Officer Cindy Oldham.

Authorities evacuated a half-mile (805-metre) area around the spill, which took place in Paulsboro, New Jersey, just across the Delaware River from Philadelphia.

The waterway was closed as well, the Coast Guard said.

State police said at least 18 contractors working in the area complained of respiratory distress.

The U.S. Coast Guard was working with the state Department of Environmental Protection to assess the situation.

Television images of the scene on CNN showed several cars partly submerged in the creek. One car was shown at a near-vertical angle from the bridge bed into the water.

Conrail is jointly owned by rail operators CSX Corp. and Norfolk Southern Corp..

(Reporting by Edith Honan and Ellen Wulfhorst; Writing by Dan Burns; Editing by James Dalgleish, Bernadette Baum and Vicki Allen)