BRIDGEPORT, Conn. (WHDH) – Hot temperatures are having an effect on several firefighters in Bridgeport, Connecticut. They had to be treated for heat exhaustion while battling a warehouse fire.

The abandoned warehouse went up in flames on Thursday. Part of the building collapsed. Mayor Bill Finch said the design of the building, which used to house an art studio, proved to be a challenge for firefighters.

“Our fire department has done a great job of controlling the fire on the perimeters, but there's a lot of smaller, interior sections that are not reachable at this point. This particular property is multiple buildings, some as old as the 1800s. Old industrial buildings and lots of wood inside the building," said Mayor Bill Finch, Bridgeport, CT.

The mayor said several firefighters suffered from heat exhaustion and dehydration. He did not know if any were transported to the hospital.

Firefighters worked overnight to control "hot spots". At one point, a part of the building collapsed causing workers to shut down train tracks across the road.

The cause of the fire is still unknown.