The head of the Defense Ministry’s Okinawa Defense Bureau lodged a protest with U.S. forces Tuesday after a U.S. Marine Corps’ MV-22 Osprey aircraft reportedly flew over residential areas with an object suspended below it, local officials with the bureau said Wednesday.

The tilt-rotor transport aircraft, feared by many in the prefecture to be accident-prone, was confirmed as having flown above houses in the village of Ginoza around 5 p.m. on Tuesday with an unidentified cylindrical object hanging by cables from its belly, the officials said.

Koichiro Nakajima, the director-general of the ministry’s Okinawa Defense Bureau, is reported to have said such training activities cannot be tolerated.

The bureau also apologized for distress caused with residents in the village and other areas.

“It flew over repeatedly, until late evening,” said a woman who saw the Osprey fly above her home. “All I feel is fear.”

Osprey aircraft, which take off and land like helicopters but cruise like planes, have been a matter of concern in Japan for some time. The U.S. military has deployed dozens of the aircraft to the Marines’ Air Station Futenma in a densely populated area in the prefecture.

Okinawa, which hosts the bulk of U.S. military facilities in Japan, is seeking to relocate the base outside the prefecture.