— The remains of some of the 10 sailors missing since a U.S. Navy guided-missile destroyer collided with an oil tanker near Singapore have been found in compartments on the damaged ship, the commander of the Pacific Fleet said Tuesday.

The search for other missing sailors from the USS John S. McCain was ongoing.

“We’re always hopeful that there are survivors,” Adm. Scott Swift said at a news conference in Singapore. “Until we have exhausted any potential of recovering survivors or bodies, the search-and-rescue efforts will continue.”

Swift also said he had ordered a special review of naval operations at the Navy’s main bases in Japan, at Yokosuka and Sasebo, after four incidents this year off Japan and South Korea — two involving Yokosuka-based ships.

Ten sailors have been missing since the McCain and a Liberian-flagged oil tanker — more than three times the destroyer’s size — collided at the entrance to the Strait of Malacca before dawn Monday.

Search and rescue efforts are underway after the USS John S. McCain guided-missile destroyer and an oil tanker collided near Singapore on Aug. 21. The Navy reports 10 sailors are missing and five are injured. (Amber Ferguson/The Washington Post)

Singaporean and Malaysian navy ships and helicopters had joined U.S. aircraft searching for the sailors at sea. But earlier Tuesday, Navy and Marine Corps divers were sent into compartments in the damaged part of the destroyer that had been sealed to stop the ship from being flooded. The ship is moored at Changi naval base in Singapore.

“The divers were able to locate some remains in those sealed compartments during their search today,” Swift said. It was “premature” to say how many bodies had been found, he added.

“Additionally, the Malaysian navy has reported that they have located potential remains,” Swift said. It was not clear whether those belonged to one of the missing sailors. The remains were found at sea and were being transferred to the U.S. Navy for identification.

Swift said that the ship suffered “significant damage” and that investigators were seeking to piece together “what happened and how it happened.”

There was no indication of a cyberattack, he said, responding to speculation about the cause of two collisions in just over two months, but he added that every scenario will be reviewed.

Tuesday’s statement will come as a heavy blow to the Navy and particularly to the Yokosuka-based 7th Fleet.

The damaged USS John McCain is docked next to the USS America at Changi naval base in Singapore on Tuesday. (Stringer/Reuters)

Yokosuka is the home port for the McCain and the USS Fitzgerald, which was involved in a similar collision in June, leaving seven sailors dead.

The Fitzgerald collided with a container ship south of Japan, leading to significant damage to its hull and a frantic effort to seal off the damage and stop the rest of the ship from flooding. Seven sailors were trapped in their berthing compartment in the process, and all drowned.

The McCain collision was the Navy’s fourth major accident at sea in Asia this year. On May 9, a collision occurred between the guided-missile cruiser USS Lake Champlain and a South Korean fishing vessel. On Jan. 31, the guided-missile cruiser USS Antietam ran aground in Tokyo Bay near Yokosuka.

The Navy’s top admiral on Monday ordered a fleetwide review of seamanship and training in the Pacific.

The series of accidents in the Pacific “demands more forceful action,” Adm. John Richardson, the chief of naval operations, told reporters Monday, adding that there is “great cause for concern that there is something we are not getting at.” 

He ordered Navy fleets across the world to take a day or two to review procedures and training to ensure they are operating safely.

Swift said Tuesday that he welcomed the review, intended to determine whether there was a “common cause.  

“One tragedy like this is one too many, and while each of these four events is unique, they cannot be viewed in isolation,” he said, adding that the operational review will be completed by Monday .

“In addition, I have ordered a second phase that will be focused on all surface ships deployed in the Pacific, including those forward-deployed naval forces in Yokosuka and Sasebo,” Swift said. “This second phase will be a deliberate reset for our ships focused on a number of areas, such as navigation, ships’ mechanical systems and bridge resource management.”

In South Korea, the chief of U.S. Pacific Command, Adm. Harry Harris, asserted that U.S. military readiness in Asia would not be compromised by “pauses” in operations of some vessels.

“The force writ large will maintain its primary responsibility of defending our homeland,” he told reporters.

The McCain — named after the father and grandfather of Sen. John McCain (R-Ariz.) and nicknamed “Big Bad John” — is an Arleigh Burke-class destroyer that had been on its way to a routine port visit in Singapore after patrolling in the South China Sea.

The collision occurred just east of the Strait of Malacca, a 550-mile-long stretch of water between the Malay Peninsula and the Indonesian island of Sumatra, connecting the Pacific and Indian oceans. It is one of the world’s busiest shipping lanes.

The collision caused significant damage to the hull and flooded nearby compartments, including crew berthing, machinery and communications rooms, the 7th Fleet said in a statement.