YOKOSUKA, Japan — U.S. and Japanese vessels and aircraft were searching Saturday for seven American sailors who were missing after their Navy destroyer collided before dawn with a container ship four times its size off the coast of Japan.

The USS 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.

After helping stabilize the USS Fitzgerald, the destroyer USS Dewey joined other American and Japanese vessels and aircraft in the search for the missing sailors. At least three other Navy sailors were injured in the collision.

Family members were frantically seeking news, appealing via social media for calls.

The U.S. 7th Fleet said the crash damaged two berthing spaces, a machinery room and the radio room. Most of the more than 200 sailors aboard would have been asleep in their berths at the time of the pre-dawn crash.

Water was being pumped out of flooded areas and it was unclear how long it would take to get into the crushed part of the ship.