PAULSBORO, N.J. (AP) — Officials in New Jersey are backing away from an earlier claim that a bridge buckled and caused a freight train carrying hazardous chemicals to derail.

It's not clear whether the derailment or the partial collapse happened first over Mantua Creek in Paulsboro.

Environmental officials are sending a special vehicle to monitor air quality around the site of the derailment.

At least two tanker cars toppled into the creek causing a leak of hazardous vinyl chloride into the air Friday. High exposure levels can cause breathing problems and dizziness.

Dozens of people went to a hospital complaining of breathing problems.

The Environmental Protection Department says tests show no chemical in the air now.

The National Transportation Safety Board is sending a team to the site.

A barge with a crane is being brought in from New York City so it will be at least a day before the damaged tankers can be removed.