The U.S. Navy ordered a broad investigation into the performance and readiness of the Pacific-based 7th Fleet after the USS John S. McCain and an oil tanker collided in Southeast Asia, leaving 10 U.S. sailors missing and five injured.

It was the second major collision in two months involving the 7th Fleet. Seven sailors died in June when the USS Fitzgerald and a container ship collided in waters off Japan.

Vessels and aircraft from the U.S., Indonesia, Singapore and Malaysia were searching for the missing sailors. Four other sailors were evacuated by a Singaporean navy helicopter to a hospital in the city-state for treatment of non-life-threatening injuries, the Navy said. A fifth was taken to the hospital by ambulance after the destroyer arrived in Singapore under its own power, the Maritime and Port Authority of Singapore said.

“It is the second such incident in a very short period of time — inside of three months — and very similar as well,” Navy Adm. John Richardson, the chief of naval operations, told reporters at the Pentagon. “It is the last of a series of incidents in the Pacific fleet in particular and that gives great cause for concern that there is something out there we are not getting at.”

Richardson ordered a pause in operations for the next couple of days to allow fleet commanders to get together with leaders, sailors and command officials and identify any immediate steps that need to be taken to ensure safety.

A broader U.S. Navy review will look at the 7th Fleet’s performance, including personnel, navigation capabilities, maintenance, equipment, surface warfare training, munitions, certifications and how sailors move through their careers. Richardson said the review will be conducted with the help of the Navy’s office of the inspector general, the safety center and private companies that make equipment used by sailors.

There was no immediate explanation for the collision. Singapore, at the southern tip of the Malay Peninsula, is one of the world’s busiest ports and a U.S. ally, with its naval base regularly visited by American warships.

Richardson said in response to a question that there was no indication the collision was intentional on either side and that the possibility of cyber sabotage would be explored just as it was during the probe of the USS Fitzgerald collision. Later, Richardson tweeted that nothing indicated cyber intrusion or sabotage had occurred but the review will consider all possibilities.

The McCain had been heading to Singapore on a routine port visit after conducting a sensitive freedom-of-navigation operation last week by sailing near one of China’s man-made islands in the South China Sea. The collision east of Singapore between the 154-meter (505-foot) destroyer guided missile destroyer and the 183-meter (600-foot) Alnic MC ripped a gaping hole in the destroyer’s hull.

The Navy’s 7th Fleet said “significant damage” to the McCain’s hull resulted in the flooding of adjacent compartments including crew berths, machinery and communications rooms. A damage control response prevented further flooding, it said.

The destroyer was damaged on its port side aft, or left rear, in the 5:24 a.m. collision about 4.5 nautical miles (8.3 kilometers) from Malaysia’s coast but was able to sail on to Singapore’s naval base. Malaysia’s Maritime Enforcement Agency said the area is at the start of a designated sea lane for ships sailing into the busy Singapore Strait.

A photo tweeted by Malaysian navy chief Ahmad Kamarulzaman Ahmad Badaruddin showed a large rupture in the McCain’s side near the waterline. Janes, a defense industry publication, estimated the hull breach was 3 meters (10 feet) wide.

Another U.S. naval vessel, the amphibious assault ship USS America, deployed its Osprey aircraft and Seahawk helicopters to search for the missing the sailors. The ship also was helping with damage control on the McCain and providing meals and sleeping space for the crew from the damaged ship.

On Tuesday, the Navy said divers were assessing the hull damage and that the America was supporting the work on the McCain to dewater the ship and restore auxiliary systems.

One of the injured sailors, Operations Specialist 2nd Class Navin Ramdhun, posted a Facebook message telling family and friends he was OK and awaiting surgery for an arm injury. He told The Associated Press in a message that he couldn’t say what happened. “I was actually sleeping at that time. Not entirely sure.”

The Singapore government said no crew were injured on the Liberian-flagged Alnic, which sustained damage to a compartment at the starboard, or right, side at the front of the ship some 7 meters (23 feet) above its waterline. The ship had a partial load of fuel oil, according to the Greek owner of the tanker, Stealth Maritime Corp. S.A., but there were no reports of a spill.

Several safety violations were recorded for the oil tanker at its last port inspection in July, one fire safety deficiency and two safety-of-navigation problems. The official database for ports in Asia doesn’t go into details and the problems apparently were not serious enough for the tanker to be detained.

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. An investigation into how and why the Fitzgerald collided with the other ship was not finished, but enough details were known to take those actions, the Navy said.

The McCain, based at the 7th Fleet’s home port of Yokosuka, Japan, was commissioned in 1994 and has a crew of 23 officers, 24 chief petty officers and 291 enlisted sailors, according the Navy’s website.

The destroyer is named for two decorated World War II admirals who were the father and grandfather of U.S. Sen. John McCain.

(AP)