Signal glitch noted before NJ derailment NEW JERSEY

Freight train tank cars that derailed Friday are seen in Mantua Creek Saturday, Dec. 1, 2012, in Paulsboro, N.J. Residents in an area of about 12 blocks near the derailment remain out of their homes as officials continued their efforts to clear a hazardous gas that spewed from a ruptured freight train car. The precautionary evacuations were ordered late Friday, hours after a train derailment, and will likely remain in effect throughout the weekend and possibly longer. The order came after readings showed higher levels of vinyl chloride in the air. (AP Photo/Mel Evans) less Freight train tank cars that derailed Friday are seen in Mantua Creek Saturday, Dec. 1, 2012, in Paulsboro, N.J. Residents in an area of about 12 blocks near the derailment remain out of their homes as ... more Photo: Mel Evans, Associated Press Photo: Mel Evans, Associated Press Image 1 of / 4 Caption Close Signal glitch noted before NJ derailment 1 / 4 Back to Gallery

Paulsboro, N.J. -- A signal may have been malfunctioning on a southern New Jersey bridge where a train derailed, causing a hazardous chemical to spew into the air and leading to health problems and evacuations.

The train crew told investigators that when they approached the bridge Friday, the signal was red, telling them not to cross, National Transportation Safety Board chairman Deborah Hersman said Saturday.

She said the conductor got off the train and inspected the bridge. When it appeared to be OK, she said, the engineer called for - and received - permission from a dispatcher to go through the red light and cross the bridge.

Only the two locomotives and the first five cars on the train got across the bridge before seven cars derailed.

The accident ripped a hole inside one of the tankers, causing vinyl chloride gas to escape. More than 70 people went to an emergency room Friday, none with life-threatening injuries.