PAULSBORO, N.J. — A signal  problem and/or a bridge-locking defect may have been contributing factors in a Conrail bridge collapse and CSX train derailment here Nov. 30. Paulsboro is some 20 miles southeast of Philadelphia.

Some 12,500 gallons of the hazardous material vinyl chloride spilled into a creek from four derailed tank cars. There were no crew injuries. While some 60 of those in the area were treated for respiratory problems, none of the injuries was reported as serious.

News reports quote National Transportation Safety Board Chairman Deborah Hersman that there were possible problems with a track signal and/or the swing-bridge locking system.

Hersman said the CSX crew encountered a red signal, although the bridge was not in an open position to permit boat traffic on the creek below to pass. The crew, reporting the conflict, and after visually inspecting the bridge, was given authority by a dispatcher to cross the bridge, Hersman said. According to news reports, the locomotive and five cars had crossed the bridge at 8 mph when it collapsed.

Investigators from the National Transportation Safety Board are being assisted by members of the UTU Transportation Safety Team.

This is the second time the swing bridge has collapsed. In 2009, it collapsed causing the derailment of 16 coal cars of a 50-car coal train. It was repaired then and placed back in service.