Firefighters were called to the scene at about 7:30 a.m. Tim Fordham with the Los Angeles County Fire Department said the blaze appeared to have originated at the rear of the building, located in the 17700 block of Gridley Road.
Fordham said the facility housed a total of nine patients. After all patients and staff members were evaluated by emergency personnel, Fordham said four males and two females were transported to area hospitals.
Of the six, two cases were categorized as needing advanced life support. Those two patients were treated for smoke inhalations and minor burns, he said.
The fire was contained to a single room in the building and was knocked down within five minutes.
The cause of the blaze and damage estimates are under investigation.
