The U.S. Navy said on Thursday human remains found by Malaysia were not one of its 10 sailors missing after a collision between one of its guided-missile destroyers and a merchant vessel east of Singapore this week.

Medical examination of the remains, which the Malaysian navy discovered about eight nautical miles northwest of where the USS John S. McCain and a merchant vessel collided on Monday, confirmed it was not one of the 10 sailors, the U.S. Seventh Fleet said in a statement. The body would be returned to Malaysian authorities.

An international search-and-rescue operation involving aircraft, divers and vessels is looking for the missing sailors over an area of about 5,500 square kilometres around the crash site.

On Tuesday, U.S. Navy and Marine divers found remains of missing sailors inside sealed sections of the damaged hull of the John S. McCain, which is moored at Singapore's Changi Naval Base. The Navy has not announced the identity or number of those found in the ship.

Four sailors injured in the crash left a Singapore hospital on Wednesday and have returned to duty, the U.S. Seventh Fleet said.

The commander of the Seventh Fleet was relieved of duty Wednesday following two collisions and two other incidents this year that raised questions about its operations in the Pacific.

The firing of Vice Adm. Joseph Aucoin, a three-star admiral, was a rare dismissal of a high-ranking officer for operational reasons.

Seven sailors died in June when the destroyer USS Fitzgerald collided with a container ship off Japan.

The Seventh Fleet, headquartered in Japan, operates as many as 70 ships, including the U.S. Navy's only forward-deployed aircraft carrier, and has about 140 aircraft and 20,000 sailors.