According to the Asahi Shimbun newspaper, the blaze hit a building where hazardous materials are stored and processed.
Kadena is the biggest US air base in Okinawa, covering 2,000 hectares (4,942 acres) and having two 3,700 meter (1,2139 feet)-long runways.
Okinawa prefecture represents only 0.6 percent of Japan's territory but hosts over 70 percent of US military facilities in the country. According to the administration of the prefecture, 25,800 US personnel are stationed in Okinawa, along with 19,000 family members and civilians.
Meanwhile, Okinawa residents have long been seeking a reduction in US military presence.