Ten Navy sailors are missing following a collision between the USS John McCain and an oil tanker off the east coast of Singapore.

The McCain docked at Singapore’s naval base early Monday with “significant damage” to its hull following the accident with the Alnic MC.

Aircraft and vessels from the U.S., Indonesia, Malaysia and Singapore are currently searching for the missing American personnel.

The collision is the second involving a ship from the U.S. Navy’s 7th Fleet in the Pacific in two months.

The McCain, which is a guided missile destroyer, had been heading to Singapore on a routine port visit following a sensitive freedom-of-navigation operation last week.

The destroyer sailed near one of China’s man-made islands in the South China Sea, which is the subject of multiple territorial disputes in the region.

The Navy’s 7th Fleet said damage to the McCain’s hull flooded adjacent compartments including crew berths, communications rooms and machinery.

The vessel was damaged on its port side aft, or left rear, around 5:24 a.m. local time before heading to port.

The Navy’s 7th Fleet added that a damage control response prevented additional flooding to the craft.

Four U.S. sailors were evacuated by a Singaporean navy helicopter to a hospital there, according to the Navy.

A fifth injured sailor did not require further medical attention following the incident, the Navy added.

Operations Specialist 2nd Class Navin Ramdhun posted a Facebook message Monday telling loved ones he is alright and waiting surgery for an arm injury.

“I was actually sleeping at the time,” he told The Associated Press of the collision. “[I’m] not entirely sure [what happened].”

Singapore’s government said that no crew members aboard the Alnic, a Liberian-flagged vessel, were injured.

An official database for ports in Asia said the Alnic was last inspected in the Chinese port of Dongying on July 29.

The Alnic had one document deficiency, one fire safety deficiency and two safety of navigation problems.

Singapore is one of the globe’s busiest ports, and the Asian nation’s naval base is often visited by U.S. warship as it is a key American ally.

President Trump tweeted Sunday that he is sending “thoughts and prayers” to the sailors abord the McCain while the search and rescuse operation unfolds.

Sen. John McCain (R-AZ), who grandfather and father’s names inspired the destroyer’s, added that he and his wife are also thinking of the sailors affected by the collision.