The derailment happened around 7:00 a.m. Friday near North Commerce Street.
Four train cars fell off the bridge and into the water below.
Authorities say the train was transporting vinyl chloride. At this time, it's not clear if any of the chemical made it into the river water.
The New Jersey Department of Environmental Protection said their preliminary information on the cars that hit the water is that one rail car had vinyl chloride and one rail car had propane.
According to the EPA's website, short-term exposure to vinyl chloride can cause dizziness, drowsiness, and headaches.
Long-term vinyl chloride exposure has been shown to increase the risk of a rare form of liver cancer, the EPA says, and has classified vinyl chloride as a Group A human carcinogen.
Everyone in nearby Paulsboro High School is being kept in the school - no one is permitted to leave and no one is allowed to enter the school at this time.
The same shelter policy has been put in place for the entire area, in an effort to keep nearby residents indoors.
However, there are no reports of evacuations at this time.
Stay with Action News and 6abc.com as more information becomes available.
Online: Vinyl Chloride info on EPA.gov