CHATTANOOGA — Chattanooga firefighters responded to a fire at a vacant convenience store with attached vacant apartments this morning.

The structure was at 6234 Bonny Oaks Drive.

Battalion Chief Steve Swanson said the whole backside of the building was engulfed in flames when firefighters arrived around 2 a.m.

Damage was extensive but an estimate on the dollar loss was not available. No injuries were reported.

Eyewitnesses told firefighters that they heard an explosion before the fire. The cause is under investigation.