TOKYO -- Seven U.S. Navy sailors are missing after the USS Fitzgerald destroyer collided before dawn with a container ship four times its size off the coast of Japan, CBS News national security correspondent David Martin reports.

A spokesman for the 7th Fleet said U.S. and Japanese aircraft continue to search for the missing sailors. The collision occurred at 2:30 a.m. local time about 56 nautical miles off the coast of Yokosuka, Japan, which is home to the 7th Fleet.

The Fitzgerald was back at its home port in Yokosuka Naval Base south of Tokyo by sunset Saturday, its crew lined up on deck. The Philippine-flagged container ship was berthed at Tokyo's Oi wharf, where officials began questioning crew members about the cause of the nighttime crash.

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The seven sailors were thought to have been thrown into the sea or possibly trapped inside damaged sections of the destroyer, said Japanese coast guard spokesman Yoshihito Nakamura.

Thoughts and prayers with the sailors of USS Fitzgerald and their families. Thank you to our Japanese allies for their assistance. https://t.co/d1l5ctjNyB — Donald J. Trump (@realDonaldTrump) June 17, 2017

The Fitzgerald was struck by the Philippine-registered container ship ACX Crystal. The Philippine ship is 29,060 tons and 730 long, the coast guard said, much larger than the 8,315-ton naval destroyer. Aerial television news footage showed its bow on the left side was dented and scraped, but it did not appear to have suffered any major structural damage.

US Navy guided missile destroyer USS Fitzgerald arrves at its mother port US Naval Yokosuka Base, Kanagawa prefecture on June 17, 2017. The US and Japan launched a major search operation to find seven missing American sailors on June 17 after their navy destroyer collided with a container ship, crushing the side of the military vessel. / AFP PHOTO / Kazuhiro NOGI (Photo credit should read KAZUHIRO NOGI/AFP/Getty Images) Kazuhiro Nogi / AFP/Getty Images

The area is particularly busy with sea traffic, said Yutaka Saito of the coast guard.

Japanese vessels first arrived on the scene and the coast guard is leading the search. U.S. aircraft is assisting in the effort, along with several Japanese helicopters and one plane, the 7th Fleet said.

The collision injured the vessel "above and below the water line, causing significant damage," the 7th Fleet said.

The Fitzgerald, an Arleigh Burke-class guided missile destroyer commissioned in 1995, is based in Yokosuka, according to the Navy. Its crew typically includes 23 officers, 24 chief petty officers and 291 enlisted sailors.

The Fitzgerald's captain, Cmdr. Bryce Benson, was airlifted to the U.S. Naval Hospital in Yokosuka and was in stable condition, the 7th Fleet said in a statement. Two other crew suffered cuts and bruises and were evacuated, it said. It was unclear how many others may have been hurt.

The Fitzgerald had limited propulsion after suffering damage on the right side below the water line and a U.S. defense official said there was flooding in three compartments. It wasn't clear yet what caused the nighttime collision between the destroyer and the container ship four times its size. Most of the more than 200 sailors aboard would have been asleep in their berths, some of which were reportedly flooded.

The Navy, Japanese maritime defense vessels and the coast guard were working to stabilize the destroyer as it headed to shore, said Navy chief Adm. John Richardson.

"Right now we are focused on two things: the safety of the ship and the well-being of the sailors," said Adm. Scott Swift, commander of the U.S. Pacific Fleet.