The window of a U.S. military helicopter fell onto the sports field of an elementary school in Japan on Wednesday, injuring one child.
The student was slightly injured by gravel thrown up after the metal framed window struck the playground, according to Japanese news agency Kyodo.
The school is located next to the U.S. Marine Corps Air Station Futenma on the island of Okinawa. Relations between locals and the base are already strained following previous military accidents, crimes linked to U.S. soldiers and noise pollution.
The Sikorsky CH-53E Super Stallion is the largest and heaviest helicopter in the U.S. military. The incident rate of its Navy version has previously been criticized.
United States Forces in Japan issued a statement describing the event as a "regrettable incident" and apologized for any anxiety it caused. The military release said the window fell from the helicopter at 10:09 a.m. local time (8:09 p.m. ET Tuesday).
The latest incident follows another in October when a CH-53E based out of Futenma crashed in the Takae district of Okinawa. No one was injured, but locals were angered when flights resumed just one week later.
Relations between the U.S. military and Okinawa locals have been under stress for more than a decade.
Following a 1995 rape of a local girl by three American servicemen, the U.S. agreed to move away from the Futenma base. However, locals have been angered by slow progress as well as a deal to move the base to another part of the island.
Anger exploded again in 2016 when Japanese authorities charged a former marine and U.S. military contractor with the rape and murder of a 20-year-old woman in Okinawa in April 2015.
The man was sentenced to life in prison on Dec.1.