Several rail cars tumbled into a creek in Paulsboro, N.J., on Friday, when a freight train derailed and released vinyl chloride into the air, sickening dozens of local residents. Reuters

PAULSBORO, N.J.—A freight train derailed Friday on a bridge in this southern New Jersey town south of Philadelphia, sending several tanker cars tumbling into a creek and releasing into the air a hazardous chemical that sickened dozens of local residents.

More than a hundred residents were evacuated from Paulsboro, N.J., Friday night following a train accident earlier in the day that leaked hazardous chemicals into the air and a nearby creek. The bridge was also the site of an accident in 2009.

The accident occurred on a bridge operated by Consolidated Rail Corp., known as Conrail, above a creek that flows into the Delaware River across from Philadelphia International Airport. Officials said four tanker cars overturned into the creek, and one containing vinyl chloride ruptured and leaked.

Residents described a fog-like gas that settled on the area after the accident. Forty-two people were treated at Underwood-Memorial Hospital, in nearby Woodbury, for respiratory ailments, according to a hospital spokeswoman. A Gloucester County official said none of the injuries was serious.

Officials said there was no sign that the toxic material leaked into the Mantua Creek, but they were using containment booms as a precaution.

Vinyl chloride is a raw material used in the making of plastic and vinyl products, and if the chemical is inhaled, it can inflame the trachea, lungs and other parts of the respiratory system, according to Philip J. Landrigan, an occupational-medicine expert at Mount Sinai School of Medicine in New York. But isolated exposure to the chemical hasn't been shown to cause permanent respiratory problems, he said.

The gas also is flammable, Dr. Landrigan said, and because it is heavier than air, it can form pockets in low-lying areas. But wind typically disperses the gas to safe levels quickly, he said. The Environmental Protection Agency said the gas at the train-wreck site had already dispersed.

A freight train derailed Friday morning over a creek in Paulsboro, N.J., putting the town and local schools on lockdown as officials sought to contain a spill of hazardous materials. Jerry DiColo has details on The News Hub. Photo: AP.

A train derailment in Paulsboro, NJ, on Friday left a tank car leaking hazardous vinyl chloride in Mantua Creek. Photo: AP Images.

Emergency crews stabilized the leak, but the removal of the train will take several days and could be complicated by the risk of causing a further leak, said Gloucester County Freeholder Director Bob Damminger. "The site is rendered safe as of now," Mr. Damminger said.

Officials said it wasn't clear what caused the derailment, though they said the bridge was damaged. The bridge was the scene of two earlier accidents, including one three years ago, when the structure buckled under the weight of a freight train loaded with coal, according to the Gloucester County Times. In 1999, two Conrail freight cars carrying liquid propane gas derailed and tipped over on the bridge, resulting in the evacuation of nearby homes.

The chairman of the National Transportation Safety Board, Debbie Hersman, said at a news conference that the board was reviewing records of the earlier incidents. A Conrail spokesman said the company was working with officials and helping residents who sought medical care.

After the leak was discovered, emergency officials told residents to stay indoors and forced businesses to lock up with customers inside early Friday. The lockdown was lifted later Friday.

Jacqui and Daryl Benjamin, who live near the crash site with their 4-year-old son and 10-week-old child, said they were sickened by fumes and treated at the hospital and released. Ms. Benjamin said when they saw the gas fumes, they first thought it was fog. "You couldn't see the cars across the street.…You can't even see the creek and we always see the creek every morning," Ms. Benjamin said.

—Danny Gold, Christopher Weaver and Jennifer Weiss contributed to this article.

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