Kyodo/Reuters
A Japan Coast Guard vessel and a helicopter conduct search and rescue operation at the site where a U.S. military aircraft MV-22 Osprey crashed into the sea off Yakushima Island, Kagoshima prefecture, western Japan November 29, 2023, in this photo taken by Kyodo.
Tokyo CNN  — 

Search and rescue operations are underway after a US special operations aircraft crashed off the shore of Japan’s Yakushima Island on Wednesday.

The aircraft, an Air Force CV-22B Osprey assigned to the 353rd Special Operations Wing, was carrying eight airmen when it experienced an “aircraft mishap” during a “routine training mission,” according to Air Force Special Operations Command.

A spokesperson for the Japanese Coast Guard told CNN at least one person was killed in the crash, though US officials have not confirmed that information. The status of the crew is unknown. A US military official told CNN Wednesday morning that family notifications of the crash were ongoing.

“Emergency personnel are on scene conducting search and rescue operations,” Air Force Special Operations Command said in a release. “The cause of the mishap is currently unknown.”

View this interactive content on CNN.com

The Japanese Coast Guard was notified of the crash at roughly 2:47 p.m. local time, the spokesperson said. Since the crash, the government of Japan’s Okinawa Prefecture has requested to ground all Ospreys on the island chain, though the US military official said no stand-down has been ordered thus far.

“Given the concerns over the danger of Ospreys, as such unexpected incident became a reality, the only thing I can say is I regret it very much,” Okinawa Gov. Denny Tamaki said at a news conference.

The aircraft can conduct long-range infiltration, exfiltration and resupply missions for special operations forces. It can conduct missions that would require both rotary-wing and fixed-wing aircraft.

The Osprey has a history of mechanical and operational issues that have resulted in service member fatalities dating back to 1992. Wednesday’s crash comes just months after three US Marines were killed while flying in a MV-22B Osprey during a military exercise in Australia.

But statistically, the V-22’s mishap rate is lower than other aircraft. Marine aviation spokesman Maj. Jorge Hernandez told Marine Corps Times in 2022 that the Marine variant of the aircraft, the MV-22, had a mishap rate of 3.16 per 100,000 flight hours.

Wednesday’s incident also comes roughly two weeks after five Army special operations aviators were killed in a training flight crash in the eastern Mediterranean Sea.

This story has been updated with additional details.