U.S. forces said Monday that the remains of five people and the main part of a U.S. military Osprey aircraft that crashed last week in waters off southwestern Japan were discovered underwater during a joint search operation with Japan for the missing crew.

Along with another crew member whose death has already been confirmed, the current death toll of six already makes it the deadliest accident involving U.S. Ospreys, according to the Japanese Defense Ministry.

The remains of two were "successfully recovered" near Yakushima Island in Kagoshima Prefecture, the U.S. Air Force Special Operations Command said in a release, with recovery efforts continuing for the other three.

A Japan Maritime Self-Defense Force vessel conducts a search on Dec. 4, 2023, for a U.S. military CV-22 Osprey aircraft that crashed on Nov. 29 off the island of Yakushima in the southwestern Japan prefecture of Kagoshima. (Kyodo) ==Kyodo

"There is an ongoing combined effort to recover the remaining crew members from the wreckage," the command said, adding that positive identifications "have yet to be determined and will be released at a later date."

Some pieces of the wreckage from the CV-22 tilt-rotor aircraft, which went down Wednesday with eight people aboard during a training exercise near the island, were collected by the Japan Coast Guard and fishermen and have been handed over to the U.S. military.

Two others remain unaccounted for.

The latest incident marked the first-ever fatal accident in Japan involving an Osprey, rekindling concerns over the safety of the airplane. The cause of the accident is not yet known.

The crashed aircraft was one of the six U.S. CV-22 transport aircraft assigned to Yokota Air Base in the western suburbs of Tokyo, according to the Japanese Defense Ministry.

It was heading to the Kadena Air Base in the southern island prefecture of Okinawa from the U.S. military base in Iwakuni in Yamaguchi Prefecture, western Japan, according to the coast guard.

The U.S. military has said its nuclear-powered aircraft carrier Carl Vinson and other assets have joined in the coast guard and the Self-Defense Forces' searching efforts, apparently in a bid to deter China from taking provocative actions by capitalizing on the accident.

Yakushima Island is a part of the southwestern Nansei island chain, where Japan has been strengthening its defense capabilities, together with its ally, the United States, to tackle China's growing maritime assertiveness in nearby waters.

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