Joliet firefighters took several hours fighting a fire at a commercial building on the corner of Eastern Avenue and Washington Street near downtown Joliet.

The Joliet Fire Department responded to a report of a structure fire at about 2:19 p.m. Thursday, with people possibly trapped, at 1 S. Eastern Ave., the fire department said.

The initial reports were of four to five people trapped inside the building, the fire department said, Upon arrival, crews were met by four people outside the building who said that everyone was out, the department said.

Company 1 arrived to find a one-story brick commercial structure with heavy black smoke coming from the windows on the east side of the building, the fire department said.

As crews stretched their initial hose line to the front door, an explosion occurred on the east side of the building, the department said.

Conditions around the building changed immediately as heavy black smoke began pouring out of the building and the fire extended through the roof, the department said.

[ PHOTOS: Building fire downtown Joliet ]

“We began a defensive operation over the next five hours flowing water into the building. A 2-11 alarm was requested to bring more equipment to the scene,” the fire department said in a news release Thursday night.

Crews remained on the scene for over six hours. No injuries were reported, the department said.

A crew of firefighters is remaining on the scene overnight extinguishing hot spots as the building is taken down, the department said.

Fire crews from stations 1, 3, 4, 5, 6, and 8 responded to the scene. The cause of the fire is under investigation.