PAULSBORO, N.J. (AP) — A signal may have malfunctioned on a southern New Jersey bridge where a train derailed, causing a hazardous chemical to spew into the air and leading to health problems, an evacuation, tricky cleanup decisions and broader questions about the condition of railway infrastructure.

No serious injuries were reported in the Friday morning accident. But the U.S. Coast Guard said Saturday night that the evacuation of 12 city blocks near the Mantua Creek site would remain in effect as a precaution. Teams also were monitoring the air quality and collecting water samples, the Coast Guard said.