The National Transportation Safety Board on Monday released its preliminary report on a New Jersey train derailment that caused a leak of 180,000 pounds of a hazardous material, but it doesn't say what caused the accident.
The report says that readings from a data recorder showed the train was moving at 7 mph when it derailed on a swivel-style rail bridge overt Mantua Creek in Paulsboro, a community across the Delaware River from Philadelphia International Airport, on Nov. 30.
That is below the speed limit of 10 mph on the bridge.
NTSB chairman Deborah Hersman has previously said the agency is also looking into the mechanisms that lock the bridge into place.
Monday's preliminary report was silent on that, and on some other issues Hersman raised in briefings during the week she and investigators spent in southern New Jersey after the accident.
She said then that the signal light was red, but that the train's crew got permission from a dispatcher to go through anyway. She said the light would be green only if all four locking mechanisms on the bridge were fully secure. A coal train derailed on the same bridge in 2009 because of a track misalignment.
A tanker car ruptured in last month's accident, releasing vinyl chloride into the air, leading to the evacuation of more than 300 families and businesses. The NTSB said that 22 Paulsboro residents and the train conductor were treated and released at hospitals - some 50 less than one hospital initially reported.
Short-term exposure to vinyl chloride, which is used to make PVC, can cause breathing problems and dizziness. Long-term exposure has been linked to cancer.
The final derailed car was removed over the weekend.
In the report, Conrail, which owns the train, said it had spent $721,000 in damages from the accident. Much of that was to put up evacuated residents in hotels and provide them with food and other necessities.