Transcript for Another violent collision involving a Navy destroyer

onto other news tonight and that disaster at sea involving a U.S. Navy destroyer. Sailors missing, and the question, how did it happen again? The "Uss John S. McCain" colliding with an oil tank in the waters off the coast of Singapore. Ten sailors are missing tonight. Even more troubling, it's the second collision for a ship in just two months. Here's ABC's senior foreign affairs correspondent, Martha Raddatz tonight. Reporter: Tonight, the crippled "Uss McCain" is in port at a naval base in Singapore, while searchers work to find those ten missing sailors. And the Navy scrambles to find the cause of this latest accident. The gaping hole in the ship's hull giving only a hint of the horror that took place inside. It's an intolerable and inexcusable tragedy. Reporter: It was before dawn when the destroyer, one of the most sophisticated ships in the Navy, collided with the oil tanker in a busy shipping lane in the south China sea. The bulbous nose of the tanker piercing the destroyer's left side, which would be near berthing areas for the crew. In addition to those missing, five sailors were injured, four medevaced to a hospital in Singapore. It is the fourth Navy mishap this year. The second major collision for the 7th fleet in two months. Seven sailors died in June when the "Uss Fitzgerald" collided with a container ship off the coast of Japan. What have we missed? Has something changed in the environment? Are radars and we're only relying on radars and not basic seamanship? Reporter: The senior officers on the "Uss Fitzgerald" have been relieved of duty, and the Navy announced all operations will be halted for the next several days for the entire fleet. This trend demands more forceful action. As such, I direct an operational pause be taken in all of our fleets around the world. And Martha Raddatz with us live tonight, and Martha, this is not only a human tragedy with these sailors still missing tonight, but this leaves the Navy now without two ships in the pacific, at such a critical time. Reporter: It does, David. You now have $2 billion warships out of commission all coming at a time of tension with China, and when North Korea is threatening the U.S. And its allies with what it says are nuclear-tipped missiles, David. All right, Martha Raddatz with us on a Monday night. Martha, thank you.

This transcript has been automatically generated and may not be 100% accurate.