One unconscious person was found in the sea and later declared dead after the aircraft crashed off the island of Yakushima on Wednesday but none of the other seven on board have been found.

"No clues regarding the missing persons were obtained," the coastguard said in a statement issued after nightfall on Thursday, more than 24 hours after the incident.

Rescue teams conducted a dive search on Thursday after sonar detected an underwater object "but only rocks were found on the seabed," the statement said, adding that the operation would continue on Friday.

US Air Force Special Operations Command said the CV-22B Osprey was on "routine training mission" out of Yokota Air Base in Japan, with the "cause of the mishap... currently unknown".

An emergency management official in the Kagoshima region where the crash took place said police had received information that the aircraft had been "spewing fire from a left engine".

Photos released by the coastguard showed what appeared to be an overturned yellow life raft and other debris in the water off Yakushima, which lies south of Japan's southernmost main island of Kyushu.

Other photos later showed what appeared to be parts of the aircraft including part of a propeller from a fishing boat into a quay.

The major search operation on Thursday involved six patrol ships and two aircraft as well as police and local rescuers.

- String of crashes -

The Osprey, developed by Bell Helicopters and Boeing and which can operate like a helicopter or a fixed-wing plane, has suffered a string of fatal crashes.

In August, a crash in northern Australia killed three US marines while four more died in another crash in Norway last year during NATO training exercises.

Three Marines died in 2017 when another Osprey crashed after clipping the back of a transport ship while trying to land at sea off Australia's north coast.

And 19 Marines died in 2000 when their Osprey crashed during drills in Arizona.

- Grounded -

In 2016, an MV-22 Osprey crash-landed off Okinawa, prompting the US to temporarily ground the aircraft in Japan after the accident sparked anger among locals.

On Thursday, Defence Minister Minoru Kihara said he had asked the US military to suspend flights again following the latest crash.

Japan requested that US forces cease Osprey flights until their "safety is confirmed, except for search and rescue operations", Kihara said before a meeting with Ricky N. Rupp, US Forces Japan commander.

The US military, which has around 54,000 personnel in Japan, was yet to comment on the suspension request.

Government spokesman Hirokazu Matsuno said Japan's military had already suspended flights of its own Ospreys "until safety is confirmed" while expressing condolences over the crash.

"I saw the Osprey fly toward the Yakushima airport and then start rotating once or twice. Soon after, orange light radiated off... it, and barely 10 seconds passed before it fell into the ocean. A column of water maybe 50 or 100 metres high (165-330 feet) splashed up," fisherwoman Kayo Ito told broadcaster NHK.

"I can only imagine how much bigger of a disaster it might have been had the Osprey crashed into a ship or nearer the island. (The incident) worries me," she said.

kh-tmo-stu/sn

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