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 air and water, authorities said.
One of four tanks of the freight train carrying vinyl chloride fell into Mantua Creek, and its contents leaked into the waterway, which feeds into the Delaware River near Philadelphia, according to the New Jersey Department of Environmental Protection.
Some 22 people were taken to a nearby hospital for precautionary examinations and were doing fine, said Larry Ragonese, a DEP spokesman who said the health danger and environmental impact was minimal.
"Initially there was a release of gas into the air that affected some nearby residents and people working right in that area," he said.
Exposure to vinyl chloride, a highly toxic and flammable industrial chemical, can cause burning eyes or respiratory discomfort, he said.
Authorities evacuated a half-mile (805-metre) area around the spill, which took place at about 7 a.m. EST (1200 GMT) in Paulsboro, New Jersey, just across the Delaware River from Philadelphia, the U.S. Coast Guard said.
Local schools were closed and students were sent home, authorities said.
The leak was contained and no longer posed a threat, and authorities were using booms to trap the chemical in the water, Ragonese said.
At the scene, one of the freight cars was nearly vertical, nose-down and partly submerged in the creek. Other cars lay jumbled on the embankment.
"It's part of living in Paulsboro, with refineries and trains. We accept it," said resident John Diamond, 53, who was taking photographs at the scene.
The area is thick with chemical plants, and two refineries, PBF Energy's Paulsboro and Nustar's Asphault, are nearby.
Locals fish and go crabbing and jet-ski in the creek in the warm months, Diamond said.
Air quality monitors in the area did not register any problem, said Lawrence Hajna, also with the state DEP.
"All the levels are coming in within our safety range," he said.
The swing bridge that collapsed underwent extensive repairs after getting damaged in a 2009 derailment of a coal freight train, said John Burzichelli, a state assemblyman and former mayor of Paulsboro.
New Jersey State Senate President Steve Sweeney, also on the scene, said a nearby homeowner reported hearing a "loud bang" from the bridge about two days ago, and Burzichelli said Conrail had come out to examine it in response.
"That bridge is very old. It's not a good day for Conrail," Burzichelli said.
Conrail officials could not be immediately reached for comment. Sweeney said he too was having trouble getting in contact with Conrail.
Conrail is jointly owned by rail operators CSX Corp and Norfolk Southern Corp.
The U.S. Coast Guard was responding to the accident along with the DEP.