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 Japan early Saturday evening, its bridge listing to its right as it sat in the harbor at Yokosuka Naval Base, south of Tokyo. The ship was flanked by two tug boats that had helped it get back to port, and crew members could been seen on deck, waiting to disembark.

The destroyer USS Dewey helped stabilize the USS Fitzgerald after it collided with the Philippine-flagged container ship, and then joined other American and Japanese vessels and aircraft searching for the missing crew members.

At least three Navy sailors were injured, in addition to the seven missing.

Family members were frantically seeking news, appealing via social media for calls from sailors aboard from the ship.

The U.S. 7th Fleet said in a statement that 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 mid-right side of the ship once it was at the pier in Yokosuka, it said.

The ship’s captain, Cmdr. Bryce Benson, was airlifted early Saturday to the U.S. Naval Hospital in Yokosuka and was in stable condition with a head injury, the Navy said. Two other crew members suffered cuts and bruises and were evacuated. It was unclear how many others may have been hurt.

The Navy said that the collision occurred 56 nautical miles (103 kilometers) southwest of Yokosuka, home to the 7th Fleet.

“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.

An investigation was underway to determine what caused the nighttime collision between the destroyer and the container ship.

The Japanese Coast Guard said it was questioning crew members of the Philippine-registered container ship ACX Crystal to investigate the cause of the collision. The ship, operated by the Japanese shipping company Nippon Yusen K.K., arrived at Oi pier in Tokyo Bay on Saturday afternoon.

Officials are investigating the case as possible professional negligence, said Masayuki Obara, a regional official with the Japanese coast guard.

Conditions were clear at the time of the collision, though Yutaka Saito of the coast guard said the area is particularly busy with sea traffic.

The coast guard said it received an emergency call from the ACX Crystal reporting the collision at around 2:20 a.m. (1720 GMT Friday).

The names of the missing sailors were being withheld pending notification of their families. U.S. Navy personnel set up support and counseling services to help families as they sought updates on crew members.

“Just heard the sweetest voice and saw a wonderful face. He’s okay. Thank you all for the prayers,” Rita Schrimsher of Athens, Alabama, tweeted after speaking with her 23-year-old grandson, Jackson Schrimsher, via Facetime.

“It could have been worse, so we’re grateful,” she said by phone.

The Philippine ship weighs 29,060 tons and is 222 meters (730 feet) long, the coast guard said, much larger than the 8,315-ton Navy destroyer. The container ship’s left bow was dented and scraped, but it did not appear to have sustained any major structural damage.

Nippon Yusen K.K., the Japanese shipping company that operates the container ship, said all of its 20-member Filipino crew was safe.