The U.S. Navy destroyer destroyer USS Fitzgerald collided with a merchant vessel early Saturday off the coast of Japan, causing some injuries.

Japan’s Coast Guard and the Japanese broadcaster NHK reported seven U.S. sailors were missing.

The Navy said the extent of the damage to the Fitzgerald and the personal injuries were “being determined.”

We are “currently working with the Japanese Coast Guard to conduct a [medical evacuation] via helicopter for one sailor,” the U.S. Navy’s 7th Fleet, which operates in the Western Pacific and Indian Ocean, said in a statement.

It said medical assistance, along with the USS Dewey and two Navy tugs, was being dispatched as quickly as possible. It also said naval aircraft were being readied.

The collision between the destroyer and the Philippine-flagged merchant vessel ACX Crystal happened about 2:30 a.m. local time, about 56 nautical miles southwest of Yokosuka, Japan, according to the 7th Fleet.

Live footage shot from a helicopter Saturday morning by Japanese broadcaster NHK showed heavy damage to the right side of the Navy ship, just ahead of the control tower.

The Navy said the destroyer had “experienced flooding in some spaces.” It said the Japanese Coast Guard was on the scene and providing assistance.

“The USS Fitzgerald is under her own power, although her propulsion is limited,” the Navy said.

Such collisions between two ships are rare.

VOA national security correspondent Jeff Seldin contributed to this report.