Five crew members of a U.S. Navy MH-60S helicopter that crashed in the Philippine Sea off of Okinawa's main island Saturday were rescued with the help of Japan's Self-Defense Forces, the U.S. military said late Saturday.

The helicopter went down about 170 km east of Okinawa's main island during "routine operations" at around 5:15 p.m., the military said. Three were recovered by an Air Self-Defense Force UH-60 search and rescue helicopter, and the two others were recovered by a chopper from the USS Blue Ridge fleet command ship.

All five crew members were in stable condition. Three were transported by a Japanese helicopter to Naval Hospital Okinawa for evaluation, while the two others were returned by U.S. Navy helicopter to the Blue Ridge.

The cause of the crash was not immediately clear.

Based in Yokosuka, Kanagawa Prefecture, the Blue Ridge is the flagship of the U.S. Navy's 7th Fleet. The amphibious command ship serves as an afloat command-and-control headquarters.

In a tweet from its official account, U.S. Forces Japan called the rescue mission "exceptionally well conducted."

"Thanks to the professionalism and capabilities of our Japanese allies, we were able to rescue five crew members of a U.S. Navy MH-60 Seahawk helicopter yesterday evening," it added.

The quick response comes after a spate of accidents involving the U.S. military in recent years, including the June 2018 crash of an F-15 fighter jet off Okinawa's main island.

Those incidents have sparked anger in Okinawa — a strategic outpost of U.S. military power that hosts more than half of the 47,000 American military personnel in Japan.

The military presence is a sensitive subject on the island, where many feel other parts of Japan should share the burden of hosting U.S. personnel.