DOWNEY -- A two-alarm fire destroyed a Downey commercial center Thursday afternoon, and its cause is still under investigation.

Firefighters responded to 11823 Downey Ave. at 2:11 p.m. and found a vacant dental office engulfed in flames, authorities said.

A roof collapse forced firefighters to a defensive strategy and a second alarm was requested, the Downey Fire Department said in a Facebook post. Firefighters were also hampered by downed power lines.

Firefighters from Vernon, Santa Fe Springs, Compton and L.A. County helped extinguish the blaze. The cause of the fire is still under investigation.

The building was a total loss.