SINGAPORE >> The U.S. Navy ordered a broad investigation Monday into the performance and readiness of the Pacific-based 7th Fleet after an early morning collision between the USS John S. McCain and an oil tanker in Southeast Asian waters left 10 U.S. sailors missing and others injured.

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

Chief of Naval Operations Adm. John Richardson said in a video message to the fleet today that he was “devastated and heartbroken” to hear about the collision and missing sailors.

“All of our assistance is flowing to the ship and the crew,” Richardson said. “That is our primary focus right now — the safety of the crew and the ship and taking care of their families.”

He said that Adm. Scott Swift, head of U.S. Pacific Fleet at Pearl Harbor, “is en route (to Singapore) to take charge and make sure that they have all the assistance that they need.”

Richardson noted it was the second collision in three months and the latest in a series of such incidents in the Pacific theater.

“This trend demands more forceful action,” he said. As such, Richardson directed an “operational pause to be taken in all our fleets around the world” to refocus on safety and effective operations.

Additionally, he directed a more comprehensive review “to ensure that we get at the contributing factors — the root causes of these incidents.” Adm. Phil Davidson, commander of U.S. Fleet Forces Command, has been asked to take charge of that investigation.

“He has put together a broader inquiry to look into these incidents,” Defense Secretary James Mattis said, referring to the two recent collisions and other accidents at sea. Mattis spoke to reporters in Amman, Jordan, where he is traveling.

Vessels and aircraft from the U.S., Indonesia, Singapore and Malaysia are 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.

There was no immediate explanation for the collision. Singapore, at the southernmost 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.

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 Singapore Strait, one of the world’s busiest.

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, arrived in Singapore and was helping with damage control efforts on the McCain and with the search for the missing sailors. It also will feed and house sailors from the stricken ship.

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 front of the ship some 7 meters (23 feet) above its waterline. There were no reports of a chemical or oil spill.

Singapore sent tugboats and naval and coast guard vessels to search for the missing sailors and Indonesia said it sent two warships. Malaysia said three ships and five boats as well as aircraft from its navy and air force were helping with the search, and the USS America deployed Osprey aircraft and Seahawk helicopters.

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 were apparently not serious enough for the Liberian-flagged vessel to be detained by the port authority.

The 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.

“The chief of naval operations’ broader inquiry will look at all related accidents, incidents at sea” involving ships of the 7th Fleet, Mattis said. “This is a broader look at what is happening.”

Richardson wants to ensure there aren’t bigger problems in the fleet that may be masked by the high pace of operations there and budget uncertainties, according to a Navy official. Beyond the tragedy of the lost lives and the hundreds of millions of dollars being spent on repairs, Richardson wants to be sure that the Navy is able to meet the maritime demands, particularly in the Pacific region, the official said.

Richardson has directed Adm. Phil Davidson, head of the Navy’s Fleet Forces, to lead the investigation. Davidson will assemble a panel of officers to help with the investigation and will have the full use of the Navy’s office of the inspector general as well as the safety center.

In the June collision, the Fitzgerald’s captain was relieved of his command and other sailors were being punished after the Navy found poor seamanship and flaws in keeping watch contributed to the 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.

U.S. President Donald Trump expressed concern for the McCain’s crew. Returning to Washington from his New Jersey golf club, he responded, “That’s too bad” when reporters shouted questions to him about the McCain. Later, Trump tweeted that “thoughts and prayers” are with the McCain’s sailors.

The McCain is named after U.S. Sen. John McCain’s father and grandfather, who were both U.S. admirals. It’s based at the 7th Fleet’s homeport of Yokosuka, Japan. It was commissioned in 1994 and has a crew of 23 officers, 24 chief petty officers and 291 enlisted sailors, according the Navy’s website.

McCain said on Twitter that he and his wife, Cindy, are “keeping America’s sailors aboard the USS John S McCain in our prayers tonight — appreciate the work of search & rescue crews.”