A U.S. Navy aircraft carrying 11 crew and passengers crashed into the sea off Okinawa, Japan Wednesday while on the way to the aircraft carrier USS Ronald Reagan, military officials said.

The aircraft is believed to have crashed into the ocean at around 2:45 p.m. local time (00:45 ET.)

The ship, which is in the Philippine Sea, is conducting search and rescue operations, the Japan-based U.S. 7th Fleet said in a statement.

The cause of the crash was not immediately known, and the Navy did not release the type aircraft involved.

“Personnel recovery is underway and their condition will be evaluated by USS Ronald Reagan medical staff,” the statement said. “The names of the crew and passengers are being withheld pending next of kin notification.”

The aircraft was taking part in an ongoing U.S.-Japan naval exercise off the coast of Okinawa in which some 14,000 U.S. personnel were participating.

The annual exercise is "designed to increase the defensive readiness and interoperability of Japanese and American forces through training in air and sea operations," a statement on the event said earlier this month.

No further information was immediately available.

The accident comes at a time when the Navy's 7th fleet and the U.S. Pacific Command have come under increased scrutiny after two deadly collisions in Asian waters this year left 17 sailors dead.