The U.S. Marine Corps is looking into reports that a Japanese children’s nursery was struck by a cylindrical object that fell from a U.S. military helicopter Thursday morning.

Staff at the nursery in the southern city of Ginowan told a Japanese broadcaster that they heard a loud noise after an object engraved with the letters “US” struck the roof shortly after 10 a.m.

Nursery officials said no one was injured but 61 children and at least 10 staffers were on site at the time of the incident. Some of the children were reportedly playing in the yard.

Helicopters from a nearby U.S. Marine air base often fly over the nursery, according to the nursery’s principal, Takehiro Kamiya.

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A U.S. Marine spokesperson told the Daily News that American officials are investigating the incident.

“We care deeply about the safety of our friend and neighbors in the communities around which we live and operate,” the spokesperson said in a statement.