TOKYO, Aug. 18 (Xinhua) -- A fire broke out Monday morning in a seven-story building in Osaka's bustling Minami district, killing two firefighters and leaving another four injured, local media reported.

The blaze was reported around 9:50 a.m. local time from the first floor of the building housing restaurants and other businesses. Video taken at the scene showed thick black smoke and bright red flames rising violently from the riverside structure, according to national broadcaster NHK.

Fire officials dispatched 51 fire trucks and a helicopter to battle the flames. About 40 square meters, including parts of the building and an adjacent structure, were burned before the fire was brought largely under control roughly three hours later.

Police and fire authorities continue to investigate the cause of the fire. The site lies in the heart of Osaka's Minami entertainment district, a busy area crowded with tourists and shoppers. ■