A U.S. military helicopter flew over an elementary school next to an air base in Okinawa on Friday afternoon despite a promise to avoid doing so, Japanese government sources and the U.S. Forces said.
The U.S. military made the promise after a window fell from a CH-53E chopper onto the grounds of an elementary school there in December.
The Marines admitted a helicopter flew over the Futenma No. 2 Elementary School on Friday, and said an investigation has been launched.
"Although U.S. Forces voluntarily ceased flights over the school to the greatest extent possible, a U.S. helicopter inadvertently overflew the school at around 3:30 p.m. Friday," the U.S. Forces said in a statement.
"An investigation immediately began to determine the facts and circumstances surrounding the overflight in order to prevent such flights from occurring again in the future," it said.
The Defense Ministry lodged a protest with the U.S. military last month for flying helicopters over the school, but the Marines denied it then.
Local concerns have intensified over repeated accidents and mishaps involving U.S. aircraft in the southern Japanese island prefecture, where the bulk of U.S. military forces in Japan are located.