Whether the fire began during a possible robbery attempt was not immediately clear.
The fire was burning shortly after 11:30 a.m. at a two-story commercial building near the intersection of Pacific Avenue and East 57th Street.
Los Angeles County firefighters responded to the scene and were initially standing by as they waited for police to secure the scene.
The fire was extinguished by 12:15 p.m. but two suspects remained inside as an armored police vehicle was moved into position.