TOKYO, Japan (CNN) -- A worker was severely injured Wednesday when a bomb, believed to be left over from World War II, went off at a construction site in Okinawa, police said.
The impact of the explosion in the city of Itoman damaged nearly 100 windows in a nursing home near the site and wounded a 75-year-old resident, said Osamu Hamada of the city's police force.
The worker -- 25-year-old Jun Kohagura -- was at the water supply construction site when the bomb exploded, injuring him in the face.
Authorities are looking into whether the bomb was left over from World War II. Several such unexploded bombs have been found in Okinawa, "since Okinawa was the bloodiest battlefield," Hamada said.
The Battle of Okinawa, which lasted 82 days from late March through June 1945, was an Allied operation to seize the island and then use it as a springboard to invade the Japanese home islands. The battle killed some 110,000 Japanese and 12,000 U.S. troops.
Unexploded World War II-era bombs have also been found periodically elsewhere in Japan. In May, authorities evacuated more than 16,000 residents from a Tokyo suburb while they defused a one-ton unexploded bomb.
Officials believe the weapons were from a B-29 bomber that crashed in Chofu, a western suburb of Tokyo.
CNN Correspondent Kyung Lah contributed to this report.
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