The officer saw a front plate-glass window blow out, according to Det. Jim McCormack, and alerted the fire department.
Long Beach and 15 other fire departments responded to the fire, which spread through a line of adjoining businesses and caused the roof to collapse. The four-alarm blaze took about four hours to be fully contained, and extra ladder companies were called to assist.
The building was unoccupied, police said. An unknown number of firefighters were treated at the scene for minor injuries, but none were hospitalized. The destroyed businesses include a restaurant, a Chase bank, a shoe store and a women's clothing store.
Police said a six-story apartment building at the corner of Riverside Boulevard was threatened by the fire and evacuated. It was unclear if that building was damaged.
The design of the largely destroyed commercial building is known as a "cockloft." It has a shared roof with a space between the rafters and ceilings, a fire official said. There were no fire walls between the businesses. The cause of the fire is under investigation.
Written by Newsday