One person was transported to Davies Medical Center with unspecified injuries, according to police Sgt. Daryl Fong. One person was also treated at the scene for shortness of breath.
Ten people were displaced by the fire, which damaged three buildings, Fong said.
The fire, first reported to firefighters at 8:10 p.m., started at 1357-1359 Masonic Ave., according to Fire Chief Joanne Hayes-White. It spread to neighboring buildings, causing "significant damage" to 1355 Masonic Ave. and some attic damage to the building immediately uphill from the fire's origin.
Hayes-White said firefighters' jobs were made more difficult by the fact that the homes were attached.
"Fortunately it's not windy tonight," she said.
The fire was declared under control at 9:05 p.m. The cause remains undetermined at this time.
Residents in neighboring buildings were evacuated as a result of the fire, and Masonic Avenue was closed between Waller and Frederick streets.
Neighbors said the building is occupied by the landlord, who lives on the ground floor, and two couples who live in units on upper floors.
Police officers on the scene said the fire was initially reported by an elderly man who lives in the downstairs unit. The fire was being treated as a crime scene until it can be determined otherwise, according to officers on the scene.
All displaced residents are being sheltered at the Park Police Station or at a nearby residence, said Fong. The Red Cross and Animal Care and Control are on the scene to assist residents.
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