Five U.S. Marines who were missing and declared dead after a collision involving a fighter jet and another military plane off the coast of Japan last week were identified Wednesday. The Marines said that circumstances of the accident are still under investigation.

"It is with heavy hearts that we announce the names of our fallen Marines," Marine Corps Lt. Col. Mitchell T. Maury said in a statement. Maury is the commander of the Marine Aerial Refueler Transport Squadron 152, to which the five Marines were assigned.

"They were exceptional aviators, Marines, and friends whom will be eternally missed. Our thoughts and prayers remain with their families and loved ones at this extremely difficult time," he said.

Seven Marines were involved and six of those died in the accident that occurred when a KC-130 refueling aircraft carrying five crew members and an F/A-18 fighter jet carrying two others collided. Both aircraft crashed into the sea about 200 miles off the coast on Dec. 6.

This undated photo made available by the U.S. Marine Corps shows Capt. Jahmar F. Resilard. Officials announced that Capt Resilard was killed in a plane crash off the coast of Japan. U.S. Marine Corps via AP

Two Marines were rescued after the crash, one of whom, Capt. Jahmar Resilard of Miramar, Florida, later died. The Marine who survived was treated and released from the hospital, Marines spokesman Capt. Christopher Harrison said Wednesday.

The five Marines who were missing and declared dead were identified Wednesday as: Col. Kevin R. Herrmann, 38, of New Bern, North Carolina; James M. Brophy, 36, of Staatsburg, New York; Staff Sgt. Maximo A. Flores, 27, of Surprise, Arizona; Daniel E. Baker, 21, of Tremont, Illinois; and William C. Ross, 21, of Hendersonville, Tennessee.

The Marines will make every effort to salvage the aircraft and recover the bodies of the missing Marines, Maj. Eric Flanagan said in an email Wednesday.

"Every possible effort was made to recover our crew and I hope the families of these selfless Americans will find comfort in the incredible efforts made by U.S., Japanese, and Australian forces during the search," Lt. Gen. Eric M. Smith, commander of U.S. Marine Forces Japan, said in a statement Tuesday afternoon local time (Monday night ET).

The Marine Corps previously confirmed that the aircraft, both of which were assigned to units of the 1st Marine Aircraft Wing at Marine Corps Air Station Iwakuni in Yamaguchi, Japan, were conducting a training mission when the accident occurred.

Herrmann served 16 years in the Marine Corps and was promoted to lieutenant colonel posthumously. He is survived by his wife and three daughters, the Marines said.

Brophy served 12 years in the Marines and is survived by his wife, son and daughter; Flores served nine years and is survived by his wife; Baker served two years and is survived by his parents; and Ross also served two years and is survived by his mother and father, the Marine Corps said.

Aerial refueling was part of the training mission, but it is unclear whether that was ongoing at the time of the accident, Flanagan said.