Schools in Paulsboro, N.J., were ordered closed Monday after authorities detected rising levels of toxic chemicals streaming from a freight train wrecked in a derailment last week.


Investigators, meanwhile, said Conrail workers had checked a bridge just one day before it collapsed on Friday, derailing seven of the 82 freight-train cars crossing the Mantua Creek, which feeds into the Delaware River near Philadelphia.


"We have information that there were people out from Conrail working on the bridge the day before," National Transportation Safety Board Chairwoman Deborah Hersman said.


"They were doing some inspections; they were looking at the bridge," she said, noting the last recorded inspection of the track was on November 20.


Four tanker cars remained toppled into the waterway yesterday, including one with a gash that allowed vinyl chloride to escape. On Friday authorities estimated the size of leak at more than 12,000 gallons of the highly toxic and flammable industrial chemical.

An elevated reading of the hazardous chemical was detected at 6 a.m. at a local air monitoring station, prompting the shutdown of schools until further notice, Coast Guard Petty Officer Nick Ameen said.

"As a result of that the fire chief made a precautionary measure to close the schools at least for the day," Ameen said.

Exposure to vinyl chloride is known to cause a burning sensation in the eyes or respiratory discomfort.

The rail bridge is near the residential and commercial sections of the town of 6,100 people, which is also home to two oil refineries as well as chemical plants. Some 48 houses closest to the wreck were evacuated and residents will not be allowed to return to their homes before December 8, the Coast Guard said.

Hersman said the transportation inspectors would spend the next two weeks preparing a preliminary accident report.