A large fire severely damaged a building on Front Street in Dunellen late Friday night, forcing firefighters to battle the fire defensively after conditions worsened and the roof collapsed, authorities said.

The Dunellen Fire Department was dispatched around 9:55 p.m. to the 300 block of Front Street for a reported structure fire. When the fire chief arrived, heavy smoke was found throughout the second floor and flames soon vented from the attic, officials said.

Dunellen police confirmed all occupants had safely evacuated.

Crews remained on scene until about 5 a.m., when the fire appeared to be extinguished.

The cause of the fire remains under investigation by the Middlesex County Fire Marshal’s Office.

The Red Cross said they are providing emergency assistance to 14 people in four families with temporary lodging, food, clothing and other needs.

Dunellen Mayor Jason F. Cilento said on social media that no injuries were reported.