A search and rescue operation for seven missing sailors of a U.S. Navy destroyer was called off Sunday after it collided with a Philippine-flagged merchant ship, Saturday. While reports said the missing sailors were found dead, Vice Adm. Joseph Aucoin declined to confirm number of fatalities before notifying the sailors’ families.

The accident occurred southwest of the Japanese port city of Yokosuka in the early hours of Saturday morning local time, according to the Navy's 7th Fleet. The USS Fitzgerald was traveling at a speed of about 56 nautical miles to Yokosuka, when it rammed on to the container ship. The Philippine-flagged ship reportedly made a sudden U-turn about 25 minutes before the accident. It remains unclear why the sharp turn was made.

Read: Puerto Rico Ferry Fire Update: Caribbean Fantasy Cruise Line Has History Of Violations, Failed Inspections

Aucoin said the destroyer’s 116 crew members were in two berthing rooms — most likely resting at the time of the crash.

"This loss is something we all feel," Aucoin said at Yokosuka Naval Base in Japan on Sunday. "We have found a number of the remains ... of our missing shipmates, and our deepest sympathies go out to the families of those shipmates."

"There was a big puncture, a big gash underneath the waterline" along the bottom of the ship, Aucoin said.

The vice admiral added the water flow into compartments that were berthing areas for the crew was so "tremendous" that "there wasn't a lot of time in those spaces that were open to the sea."

The Fitzgerald’s captain Cmdr. Bryce Benson’s was completely destroyed, according to Aucoin.

"He's lucky to be alive," he said.

A machinery room and the radio room in the 10,000-ton destroyer were damaged. According to Aucoin, the collision left a big hole below the water line.

“As search and rescue crews gained access to the spaces that were damaged during the collision this morning, the missing Sailors were located in the flooded berthing compartments. They are currently being transferred to Naval Hospital Yokosuka where they will be identified,” the U.S. 7th Fleet said in a statement.

“The families are being notified and being provided the support they need during this difficult time. The names of the Sailors will be released after all notifications are made,” the statement read.

Read: USS Zumwalt Malfunctions In Panama Canal

Aucoin maintained the destroyer would require significant repair.

"The ship is salvageable ... [it] will require some significant repair," Aucoin said. "You will see the USS Fitzgerald back ... It will take months, hopefully under a year."

Cmdr. Ronald Flanders of the U.S. Naval Forces Japan told ABC News an investigation would be launched to determine the cause of the crash.

Four sailors were medically evacuated by a Japanese coast guard helicopter, according to Cmdr. Richard Gourley of the U.S. Naval Forces Japan. The 7th Fleet said the sailors were in stable condition and were are being treated for lacerations and wound at the Naval Hospital Yokosuka.

Meanwhile, none of the 20 crew members aboard the Philippine-flagged container ship were injured.