U.S. Army soldiers from the 1st Armored Brigade Combat Team, 3rd Infantry Division, along with Lithuanian Army and emergency services personnel, discuss a plan to recover four U.S. soldiers in an M88 Hercules submerged under several meters of water in a swamp by a training area near Pabadre, Lithuania, on Thursday. U.S. Army via AP

VILNIUS, Lithuania — Three of the U.S. Army soldiers who went missing in Lithuania have been found dead in their armored vehicle that was pulled from a swampy area early Monday, according to U.S. Army Europe and Africa Command. Another soldier is still missing.

The bodies of the three soldiers were recovered after a massive six-day effort by U.S., Polish and Lithuanian armed forces and authorities to dig the M88 Hercules vehicle out of a peat bog at the expansive General Silvestras Žukauskas training ground in the town of Pabradė.

The soldiers were on a tactical training exercise when they and their vehicle were reported missing early Tuesday, the Army said.

The command in a statement said the identities of the 1st Armored Brigade Combat Team, 3rd Infantry Division soldiers are being withheld pending family notifications.

“We stand in grief with the families and loved ones of these extraordinary ‘Dogface Soldiers’ during this unimaginable time," said Maj. Gen. Christopher Norrie, 3rd Infantry Division commander. "But the search isn’t finished until everyone is home. Words cannot express our gratitude to those still working around the clock during these extensive search and recovery efforts and your unwavering commitment not to rest until all are found.”

Hundreds of Lithuanian and U.S. soldiers and rescuers took part in the search through the thick forests and swampy terrain around Pabradė, 6 miles west of the border with Belarus. The armored vehicle was discovered on Wednesday submerged in 15 feet of water.

Lithuanian armed forces provided military helicopters, fixed wing aircraft, unmanned aerial systems and search and rescue personnel. They brought in additional excavators, sluice and slurry pumps, other heavy construction equipment, technical experts and several hundred tons of gravel and earth to help the recovery.

U.S. Navy divers were able to maneuver through thick layers of mud, clay and sediment “with zero visibility” to reach the 63-ton vehicle Sunday evening and find two points to attach steel cables, according to the command.

The command said that during the effort to pull out the vehicle, it began to lose traction, so additional heavy dozers were brought in and attached to provide additional grip. The vehicle was pulled free after about two hours, the command said.

“The armored vehicle was pulled ashore at 4:40 a.m., the towing operation is complete, Lithuanian Military Police and US investigators continue their work,” Defense Minister Dovilė Šakalienė said in a Monday morning Facebook post.

The Navy dive team now is searching the area using radar for the fourth soldier who is still missing.

Maj. Gen. Curtis Taylor, commander of Task Force Iron and the 1st Armored Division, thanked the “heroic efforts” of those involved in the search and recovery. The U.S. Army and Lithuanian authorities are investigating what caused the incident.

Lithuanian Army and emergency services personnel build a makeshift dam from HESCO barrier bags during recovery efforts for four U.S. soldiers in a U.S. Army M88 Hercules submerged under several meters of water in a swamp by a training area near Pabadre, Lithuania, on Thursday. U.S. Army via AP