CAMDEN, N.J. (AP) — A blaze erupted at a vacant chemical plant just before sunrise Sunday in one of the country's poorest cities, causing the building to partially collapse and forcing firefighters to evacuate nearby homes.

The fire at Concord Chemical Inc. in Camden, across the Delaware River from Philadelphia, comes more than a week after fires at an abandoned tire factory and a downtown warehouse.

Hazmat crews were checking to see if any chemicals were left in the former plant, which was vacated two years ago, Philadelphia's WPVI-TV reported.

The plant made detergents and cleaning products and underwent a nine-month, $1 million cleanup of asbestos and potentially explosive hazardous materials that the Environmental Protection Agency completed in May, the Courier-Post reported.

Chief Jim Jankowski with the Camden County Department of Public Safety told The Associated Press that part of the building had collapsed. No injuries have been reported, he said.

He said it was too early to say what had caused the fire, which was declared under control about three hours after it began.

Last weekend, a fire engulfed a three-story warehouse in downtown Camden. Two days earlier, a blaze consumed an abandoned tire factory and damaged several nearby row homes. At least three firefighters were hospitalized with heat exhaustion.

Those blazes are under investigation.

One resident, Iris Bones, raced home after the fire at the tire factory to check on her family. She said she often sees people around the abandoned buildings and wondered if one of them could have played a role in causing that fire.

"People are always just coming in and out of those abandoned buildings. It's a big problem," she said.

In January, the city of Camden laid off about one-third of its firefighters amid a deep fiscal crisis. Several have been hired back. But the smaller force means that reinforcements from elsewhere have to be brought in sooner, the fire chief has said.