PAULSBORO, N.J. — Homes have been evacuated anew near the spot in southern New Jersey where a train derailed, releasing a hazardous chemical into the air and sickening dozens of people.

National Transportation Safety Board chairman Deborah Hersman said Friday night that there were evacuations in Paulsboro because of increased levels of chemicals.

Around 7 a.m., seven train cars derailed on a bridge. One tanker car was sliced open, releasing vinyl chloride. Hours later, officials gave the all-clear for residents near the site to return but warned that there could be more complications.

A 12-block radius was evacuated on Friday evening. U.S. Coast Guard Lt. Drew Madjeska tells The Philadelphia Inquirer that residents might not be allowed back for several days.