This Dec. 1, 2012, photo shows a hole in one of freight train tank cars that derailed Nov. 30, into Mantua Creek 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 after readings showed higher levels of vinyl chloride in the air.
A containment boom floats in Mantua Creek, Dec. 1, 2012, near freight train tank cars that derailed in Paulsboro, N.J. A signal may have been malfunctioning on a southern New Jersey bridge where the train derailed, causing a hazardous chemical to spew into the air and leading to health problems, evacuations, tricky cleanup decisions and broader questions about the condition of railway infrastructure.
Crews continue to spray water on derailed freight train tank cars in Paulsboro, N.J., Dec. 1, 2012, after seven cars of an 84-car freight train with two locomotives derailed.
In this Nov. 30, 2012, photo, officials work the scene of derailed freight train tank cars in Paulsboro, N.J.
A containment boom floats in Mantua Creek, Dec. 1, 2012, near freight train tank cars that derailed in Paulsboro, N.J.
Crew members ride on a locomotive after leaving empty tank cars near derailed train cars in Paulsboro, N.J., Dec. 1, 2012, as crews work to pump chemicals out of the tank cars.
A locomotive backs empty tank cars towards derailed train cars in Paulsboro, N.J., Dec. 1, 2012, as crews work on the tank cars.
Displaced residents board a shuttle bus in Paulsboro, N.J., Dec. 1, 2012, as more than 100 people remain out of their homes while officials continued their efforts to clear a hazardous gas that spewed from a ruptured freight train car.
National Transportation Safety Board chairman Deborah Hersman addresses the media in Paulsboro, N.J., Dec. 1, 2012, after seven cars of an 84-car freight train with two locomotives derailed.
New Jersey state Senate President Stephen Sweeney, left, a Democrat whose district includes Paulsboro, N.J. and State Assemblyman John Burzichelli, right, a former Paulsboro mayor, listen as National Transportation Safety Board chairman Deborah Hersman answers a question in Paulsboro, N.J., Dec. 1, 2012, after seven cars of a freight train with two locomotives derailed.
State Assemblyman John Burzichelli, left, a former Paulsboro mayor, listens in Paulsboro, N.J., Dec. 1, 2012, as New Jersey state Senate President Stephen Sweeney answers, a question about the derailment of seven cars of a freight train with two locomotives.
National Transportation Safety Board chairman Deborah Hersman addresses the media in Paulsboro, N.J., Dec. 1, 2012, after seven cars of an 84-car freight train with two locomotives derailed.
Displaced residents wait for a shuttle bus outside a fire hall and community center in Paulsboro, N.J., Dec. 1, 2012, as more than 100 people remain out of their homes while officials continued efforts to clear a hazardous gas that spewed from a ruptured freight train car.