FORT WAYNE, Ind. -- (Fort Wayne's NBC News) The Fort Wayne Fire Department responded to an early morning fire on the city's south side, Monday. 

Crews arrived just before 3 a.m. to heavy smoke on the 1800 block of S. Calhoun Street at the A - Z Mercantile building.

Firefighters found a heavy fire in the ceiling on the first floor of the building. As crews worked to put out the fire, the ceiling collapsed.

One firefighter was hurt and was taken to the hospital where he was treated and released. 

It took crews more than an hour to get the fire under control.

The fire is under investigation.

Fort Wayne's NBC will continue to update this story as more information becomes available.