The US military says they presume all eight crewmembers onboard the US CV-22 Osprey that crashed into the sea off southwestern Japan last week have not survived.

The tilt-rotor transport aircraft crashed off the island of Yakushima in Kagoshima Prefecture last Wednesday.

Air Force Special Operations Command released a statement saying the recovery operation will now focus on locating and recovering all of their bodies, as well as aircraft debris.

Of the eight crewmembers, the remains of three airmen have been recovered and the remains of another three have been located and are in the process of being recovered. The remains of the other two airmen are still being located.

At the waters around the crash site, Japan's Coast Guard and others have been searching for the two crewmembers.

Parts apparently from the Osprey that were earlier retrieved from the waters have been handed over to US forces based on the Japan-US Status of Forces Agreement.

Efforts to recover wreckage are likely to continue in order to determine the cause of the crash.