A U.S. military Osprey aircraft carrying eight airmen crashed off the Japanese coast at about 3 p.m. Wednesday, U.S. officials said.
The crash took place during a "routine training mission," according to the U.S. Air Force, which added that the cause is currently unknown.
At least one airman who had been on board was located, Japanese officials said, although there was no immediate confirmation on the person's condition.
"The crew's conditions are unknown at this time," the U.S. Air Force added.
Japanese officials had previously said six people were on board the CV-22B Osprey.
The Japan Coast Guard deployed search and rescue vessels to the area off Kagoshima prefecture in southern Japan.
The wreckage of the aircraft was spotted at about 4 p.m., about an hour after the crash had been reported, in the water southeast of the airport on Yakushima Island, officials said.
The search continued into the night on Wednesday, with Coast Guard ships and helicopters active in the search area at about 7 p.m. local time.
The Osprey, a vertical takeoff and landing aircraft, or VTOL, is manufactured by Bell Boeing.
An Osprey crash in Australia in August killed three U.S. service members, Marine officials said. In June 2022, an Osprey crash killed five Marines in Glamis, California. Four U.S. Marines were killed in March 2022 in an Osprey crash during training exercises in Norway.
ABC News' Anthony Trotter and Joe Simonetti contributed to this story.