Firefighters are at the scene of a three-alarm fire burning in Santa Ana Thursday morning.
The fire was reported shortly after 5 a.m. in the 2700 block of Harbor Boulevard.
Crews were forced to take a defensive mode in attacking the blaze, the Orange County Fire Authority posted in a tweet.
Aerial video from Sky5 showed a large portion of the roof had collapsed as crews continued working to douse the fire.
The building housed multiple businesses including a dental office and a Waba Grill.
Crews appeared to have gained some access to the building as of 6:30 a.m.
The OCFA said that fire investigators had arrived at the scene in an updated tweet.
The cause of the fire remains under investigation.
There have been no injuries reported as a result of the incident.
Check back for updates on this developing story.
