Indianapolis warehouse fire under investigation

INDIANAPOLIS -- The cause of a massive four-alarm fire in Indianapolis is under investigation.

The fire started just after 9 Sunday night in an abandoned warehouse.

For more than 15-hours, 125 firefighters worked to put the fire out.

One firefighter was treated for heat exhaustion.

"They're not really sure how much structural integrity is left of this building. They're not sure what exactly was in this building or how much of this building has collapsed. So, all of those factors will play into the investigation," said an Indianapolis firefighter.

Crews evacuated about 15-homes due to flying embers. The fire also knocked out power to some houses.

The EPA is also on the scene testing air quality.