A two-day hearing on the train derailment that caused vinyl chloride to spill in Paulsboro, N.J., kicked off Tuesday in Washington, D.C.

The Conrail train released 20,000 gallons of the chemical into the air and water when several cars derailed last November.

The toxic spill forced the evacuations of Paulsboro residents over several days.

Train engineer Mark Mather testified that his crew followed proper procedure for making sure a bridge that opens and closes was safe to cross.

But he told the National Transportation Safety Board that he got conflicting messages.

"So I'd call up the train dispatcher and I'd say, 'The bridge is lined and it's locked. It's giving us a clear, but it's telling us it failed to operate,'" Mather said.

The train proceeded after the conductor physically checked that the bridge was locked; however, a red light still signaled it was not safe to cross. The derailment happened shortly after.

The NTSB reports that 24 malfunctions occurred at the bridge last year, half in the month of November.

The hearing will continue Wednesday.