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The commander of the U.S. Navy's 7th Fleet has been relieved of duty following a series of warship accidents 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 such a high-ranking officer for operational reasons.

The Navy's Pacific Fleet released a short statement Wednesday saying Adm. Scott Swift, commander of the U.S. Pacific Fleet, had relieved Aucoin "due to a loss of confidence in his ability to command."

The move follows four Navy accidents in the Pacific since late January, including two collisions that left sailors dead and missing.

On Monday, the destroyer USS John S. McCain and an oil tanker collided off Singapore, injuring five sailors and leaving 10 missing. Navy divers have found the remains of some of the missing in a flooded compartment on the ship, though specifics have not been disclosed.

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

Aucoin was due to retire in a few weeks, and the officer named to succeed him, Vice Adm. Phillip Sawyer, assumed command immediately.

Sawyer, speaking Thursday at a maritime security meeting in Bali, Indonesia, thanked the navies of Singapore, Malaysia and Indonesia for helping in the search for the missing McCain sailors.

"Often it is a brutal reminder that what we do is dangerous work in an unforgiving environment, requiring honed skills and constant vigilance," he said. "And even with those, bad things can happen."

Former 7th Fleet commander Doug Crowder told AP he cannot recall someone at that level being relieved for operational reasons.

High-ranking officers have been removed for misconduct.

Crowder, a retired vice admiral who led the 7th Fleet from 2006 to 2008, said he's sure it was a "tough call" to relieve a three-star fleet commander.

Lawrence Brennan, an adjunct law professor at Fordham University and a retired Navy officer, called Aucoin's dismissal "an unprecedented peacetime move."

"Four incidents in a short time in an operational area is a problem," he said, though he cautioned against rushing to assign blame.

The Navy has ordered an operational pause for its fleets worldwide to make sure all steps are being taken to ensure safe and effective operations. The Pacific Fleet will also carry out a ship-by-ship review of its vessels, looking at navigation, mechanical systems, bridge resource management and training.

The 7th Fleet said late Wednesday that Navy and Marine Corps divers were continuing to search the McCain, which is now docked in Singapore.

Singapore's government said the area for a sea-based search more than doubled Wednesday to about 5,500 square kilometers (2,120 square miles) with aircraft and vessels deployed by the U.S., Singapore, Malaysia, Indonesia and Australia.

At least five of the 10 missing sailors have been identified by relatives.

Crew member Logan Palmer is from the Decatur, Illinois, area and his mother identified him as missing, U.S. Rep. Rodney Davis said.

April Brandon in Michigan said the military informed her that her son, Ken Smith, is missing. She said Smith's father, stepmother and grandfather served in the Navy. Brandon said, "His father and I couldn't be prouder of our son."

The family of Jacob Drake of Ohio was told he was among the missing, the Columbus Dispatch reported. Megan Partlow told The Associated Press that Drake was her fiance and she last had contact with him Sunday in a text message.

Family members of Dustin Doyon from Connecticut confirmed that he was among the missing. Local police said the Navy was in communication with the family.

The mother of a Texas sailor said her son, John Hoagland, was among the missing and had served aboard the warship since October.

The cause of the collision has not been determined. The Navy previously said there was no evidence it was intentional, or that it was a result of sabotage or cyberintrusion.

The Navy last week said the Fitzgerald's captain was being relieved of his command and other sailors were being punished after poor seamanship and flaws in keeping watch were found to have contributed to its collision.

There were two lesser-known incidents in the first half of the year. In January, the USS Antietam guided missile cruiser ran aground near Yokosuka base, the home port of the 7th Fleet, and in May another cruiser, the USS Lake Champlain from the Navy's 3rd Fleet, had a minor collision with a South Korean fishing boat.

Aucoin, a career flight officer, served in five fighter squadrons and flew in more than 150 combat missions, according to Navy biographies. He commanded a carrier air wing aboard the USS Kitty Hawk and a carrier strike group based in Bremerton, Washington. Prior to heading the 7th Fleet, he was deputy chief of naval operations for warfare systems.

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Associated Press journalists Andi Jatmiko in Bali, Indonesia; Jennifer McDermott in Providence, Rhode Island; Lolita Baldor in Riyadh, Saudi Arabia; and Robert Burns in Amman, Jordan, contributed to this story.