Fully engulfed: What caused small explosion and fire at apartment building?

MILWAUKEE (WITI) -- Milwaukee Fire officials on Sunday afternoon, May 11th were on the scene of a fully engulfed fire that occurred at an apartment building near 92nd and Marion.

Fire officials say the fire broke out on the second floor of an apartment building -- and there was some sort of a small explosion during this fire -- as indicated by debris inside the building.

At least one of the units is a total loss.

"When the first crews arrived we had heavy fire showing out of the windows of the front, second floor apartments. The first crews got in there and knocked down the fire very quickly," Milwaukee Fire Department Battalion Chief Brian O'Connor said.

A Milwaukee Fire Department Battalion Chief tells FOX6 News one person had to be taken to the hospital with burns to the arms.

The fire has been brought under control -- but investigators remain on scene -- working to determine what may have caused this fire.

Monitor FOX6 News and FOX6Now.com for updates on this developing story.