Story highlights The CH-53 transport helicopter window fell on a school playing field

Many locals on Okinawa oppose the large US military presence on the island

Tokyo (CNN) The window of a US Marine Corps helicopter fell off mid-flight onto a school playing field, slightly injuring a child on the Japanese island of Okinawa. The incident is likely to fuel outrage among locals who view the US military footprint in southern Japan as both a pest and a danger.

US Forces Japan said in a statement that the window of a CH-53 transport helicopter fell onto a sports field Tuesday at an elementary school outside Marine Corps Air Station Futenma. The aircraft immediately returned to base after the incident.

USFJ told CNN in an email the window weighed 20 pounds (9 kilograms) and measured 35 by 34 inches (88.9 by 86.4 centimeters).

"We take this report extremely seriously and are investigating the cause of this incident in close coordination with local authorities," the statement said. "This is a regrettable incident and we apologize for any anxiety it has caused the community."

The child was not seriously injured.

The CH-53E helicopter's window that fell onto Daini Futenma Elementary School is seen in Ginowan, Okinawa prefecture.

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