US military grounds all of its V-22 Ospreys following last week's deadly crash

The U.S. military is grounding all of its Osprey V-22 aircraft in the wake of last week’s deadly U.S. Air Force crash off the coast of Japan that left eight airmen dead.

The coordinated announcement means that all versions of the Osprey flown by the Marine Corps, Air Force and Navy are being grounded as part of an operational standdown.

“Out of an abundance of caution, following the AFSOC operational stand down, NAVAIR is instituting a grounding bulletin for all V-22 Osprey variants Dec. 6. This decision comes after the V-22 Osprey mishap on Nov. 29, off the shore of Yakushima, Japan,” read statements from the Marines and Navy.

The Air Force and Marines also said in separate statements that the cause of last week’s crash is “unknown at this time,” but "preliminary investigation information indicates a potential materiel failure caused the mishap.”

“While the mishap remains under investigation, we are implementing additional risk mitigation controls to ensure the safety of our service members,” read a statement from the armed forces.

The Osprey aircraft carrying eight airmen crashed off the Japanese coast at about 3 p.m. last Wednesday, U.S. officials previously said.

The crash took place during a "routine training mission," the U.S. Air Force said last week.