U.S. Navy and Japan Maritime Self-Defense Force ships and aircraft are searching for a sailor from the destroyer USS Stethem who was reported missing today while the ship was conducting operations in the South China Sea, the U.S. 7th Fleet said.

Stethem reported a man overboard at about 9 a.m. local time, the Navy said. Multiple searches were conducted inside the ship, but the sailor could not be found. The Navy likely was extra diligent about the shipboard search after a sailor on the cruiser USS Shiloh was reported missing in June off Okinawa and then turned out to be hiding in the ship’s engineering area, officials said.

Stethem, forward-deployed to Yokosuka, Japan; USNS Amelia Earhart; USNS Vice Admiral K. R. Wheeler and a U.S. Navy P-3 aircraft are assisting in the search for the missing Stethem sailor, U.S. 7th Fleet said in a release. Japanese ships JS Izumo and JS Sazanami are searching the area along with helicopters from Izumo.

The Joint Personnel Recovery Center Hawaii is also assisting with the search, the Navy said. The sailor’s name is being withheld while the search is ongoing.

Stethem in early July sailed near Triton Island in the Paracel Islands in a freedom of navigation operation. The contested island is claimed by China, Vietnam and Taiwan.