An Air Self-Defense Force helicopter and its detached door are seen at the ASDF's Okinoerabujima Sub Base on Okinoerabujima island in Kagoshima Prefecture on March 7. (Video taken by Takahiro Kumakura)

CHINA, Kagoshima Prefecture--A 31-kilogram door fell from an Air Self-Defense Force helicopter and landed on a remote island in Kagoshima Prefecture on March 6, but no injuries were reported.

The Defense Ministry found the door on March 7 about 200 meters southeast of an ASDF sub base on Okinoerabujima island.

An investigation into the cause of the accident is under way, the ministry said.

The CH-47J transport helicopter belongs to the Naha helicopter air transportation unit of the air rescue wing of the ASDF Naha Air Base in Okinawa Prefecture.

The helicopter took off from the Naha Air Base for night drills. Around 6:50 p.m., the door, about 1.6 meters high, 2.4 meters wide and 4 centimeters thick, fell off just before the helicopter landed at the ASDF Okinoerabujima Sub Base in the town of China.

Four crew members were on board.

The dual-rotor helicopter is about 16 meters long and 5 meters wide. The lever-operated door is located at the rear of the aircraft where cargo is loaded and unloaded.

According to a 66-year-old woman who operates a coffee shop about 1 kilometer from the sub base, there are very few private houses around the site of the accident.

However, some people do agricultural work there in the daytime, she said.

SDF helicopters have caused a number of problems since February.

A Ground SDF attack helicopter crashed in a residential area of Kanzaki, Saga Prefecture, on Feb. 5.

In addition, parts believed to be from SDF helicopters have hit the ground in Osaka and Kyoto prefectures.