The rail bridge that collapsed Friday in Paulsboro also gave way three years ago, causing the derailment of nine coal cars.
The two failures in three years raised questions about the quality of freight rail bridge inspections, which are left to bridge owners.
The owners of the nation's 77,000 freight rail bridges are required to inspect their bridges at least once a year, but they need not disclose the results of those inspections.
Rail bridges "are really a massive network of blind spots for federal safety regulators," said Pat Salvi, a Chicago personal-injury lawyer who has written on rail bridge safety. "We have allowed the railroads to police themselves, the theory being that it was in their interest to maintain them well."
"The public has to be wary. . . . We're hoping and praying they're acting in good faith."
Conrail spokesman John Enright declined to comment Friday on the weight limits on the Paulsboro bridge, the bridge's recent inspection history, or the 2009 accident.
The swing bridge over Mantua Creek buckled on Aug. 23, 2009, and derailed part of a 85-car train of coal on its way to a power plant in Salem County.
The cause of that derailment was listed as "bridge misalignment or failure" on Conrail's accident report to the Federal Railroad Administration, but no cause for the bridge failure was reported.
No one was injured in that accident, and the bridge was quickly repaired by Conrail and put back into service.
State Senate president Stephen Sweeney (D., Gloucester), who represents Paulsboro, said Friday "we have a lot of questions to be answered" about the adequacy of the 2009 repair.
"Was it a temporary repair? Was it done properly? Were they going to come back and do more later?" said Sweeney, who is an ironworker by trade and has worked on bridge construction.
Since the bridge is privately owned and maintained, its inspection records are not open to the public. The Federal Railroad Administration does not regulate bridge structural safety, though the FRA monitors rail companies' bridge-inspection programs.
Holly Arthur, a spokeswoman for the American Association of Railroads, which represents freight carriers, said "bridge inspection records are to be maintained in accordance with the regulations, and repairs or modifications of bridges are governed by regulation. The FRA has the right to perform site inspections on any railroad at any time, and either announced or unannounced inspections may occur."
The FRA in 2010 issued new guidelines requiring railroads to follow specific procedures for inspecting and evaluating rail bridges.
Sweeney said Friday that state officials would look into the Paulsboro bridge's inspection history.
"There's no way they are going to be able to hide it. You know we're going to get it," he said. "I'm not pointing fingers at anybody, but this is an issue of concern."
Augustine Ubaldi, a railroad engineering expert with Robson Forensic, of Lancaster, said increased federal or state regulation would not guarantee bridge safety.
"Look at the I-35 collapse in Minnesota," Ubaldi said, referring to the 2007 highway bridge failure that killed 13 people. "There, you had a requirement for inspection reports and still something got missed."
"There seems to be the thought that if you pass a regulation, that solves all the problems. But the owner still has a responsibility to maintain the bridge, whether or not there is a requirement for a report to be filed."
Sweeney said that the Paulsboro bridge had apparently been "making noises" shortly before its collapse Friday and that "Conrail was coming out and looking at it."
Nearby homeowners said Friday that Conrail workers had been looking at the bridge for the past three weeks, but that trains had continued to operate over the span.
"Conrail people were here every day for the last three weeks," said homeowner Gary Stevenson, standing on his porch with a clear view of the tangled tanker cars.
"When the trains would go over the bridge," Stevenson said, "there would be 'bah-bum, bah-bum, bah-bum' sound. When they rebuilt it three years ago, you couldn't hear it. But then it started again."
Enright, the spokesman for Conrail, did not respond to a request for comment on the reports of noises emanating from the bridge or any recent inspections.
U.S. Sen. Frank Lautenberg (D., N.J.), chairman of the surface transportation subcommittee that has jurisdiction over rail safety, called Friday for "a thorough investigation into the cause of the accident and any impact on the environment in the surrounding areas."