A U.S. military aircraft crashed on Wednesday afternoon near a small island off the coast of Japan, leaving at least one person dead, according to a regional coast guard spokesperson.

The Japanese Coast Guard was notified about the crash, which occurred off the coast of Japan’s Yakushima Island, around 2:47 p.m. local time, as reported by NBC News.

A  news release from the Air Force Special Operations Command (AFSOC) stated that the aircraft was an Air Force CV-22B Osprey with eight crew members on board at the time of the incident.

An Osprey is a well-known aircraft that can take off and land vertically like a helicopter and fly like a turboprop plane. It is used mainly “to conduct long-range infiltration, exfiltration, and resupply missions for special operations forces,” according to the National Museum of the U.S. Air Force.

This incident comes just months after three U.S. Marines died in a crash in northern Australia involving a different-model Osprey.

“Given the concerns over the danger of Ospreys, as such [an] unexpected incident became a reality, the only thing I can say is, I regret it very much,” said Okinawa Gov. Denny Tamaki during a press conference after Wednesday’s crash, per CNN.

The AFSOC release said that the crash came during “a routine training mission,” but the “cause of the mishap is currently unknown,” along with the condition of the crew members.

Hiroyuki Miyazawa, Japan’s deputy defense minister, told reporters that the aircraft made an “emergency water landing,” adding that “The U.S. side explained to us that the pilot did his best until the very end,” as reported by NBC News.

A spokesperson from the Japanese Coast Guard confirmed to CNN that at least one crew member died during the crash, but this information has yet to be confirmed by any officials from the U.S. military.

Itsunori Onodera, a former defense minister and current legislator, posted on social media that the crash was “a worrying matter.”

“We asked the Ministry of Defense and the Japan Coast Guard to do their utmost to rescue the victims,” he wrote, as translated by the social platform.

“First, we need to rescue the crew and then request a safe flight. I hope the crew can be rescued safely soon,” he added.

No other deaths have been confirmed by either Japanese or U.S. officials, but the search and rescue process is ongoing.