The bodies of three American soldiers who had been missing since last week after their armored vehicle became trapped in deep mud during a military exercise in Lithuania have been recovered, the U.S. Army said Monday. A search for the fourth soldier remained underway.

The soldiers were aboard an M88A2 Hercules, a hulking armored recovery vehicle designed to tow tanks and other heavy machinery, when it became submerged in a bog last Tuesday, military officials said. The troops were believed to have been unable to escape as the vehicle was swallowed by the mire.

Following an arduous multinational recovery operation involving some 200 U.S., Lithuanian and Polish forces, the vehicle was extracted Sunday evening, Lithuania’s Defense Ministry said. The effort required excavators and construction machinery, as well as hundreds of tons of gravel and sand to reinforce the unstable terrain. U.S. Navy divers secured cables to the submerged vehicle, enabling crews to pull it from the mud.

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“The soldiers we have lost in this tragedy were not just soldiers — they were a part of our family,” Maj. Gen. Christopher Norrie, 3rd Infantry Division commanding general, said in a statement. “The search isn’t finished until everyone is home.”

The operation was fraught with challenges. The swampy terrain complicated efforts to drain water and excavate mud from around the vehicle. Over the weekend, the recovery effort suffered a major setback when a landslide further destabilized the ground, Lithuania’s defense minister, Dovilė Šakalienė, said on social media.

“It is highly complex trying to get to the vehicle itself with the terrain out here and where the M88 is sitting in a bog swamp-like area, below the waterline. So not only are we dealing with the terrain, a lot of mud that is over top of the vehicle, but also the fact that it’s 70 tons that we’re trying to recover out of a swamp or bog,” Brig. Gen. John Lloyd, commander of the U.S. Army Corps of Engineers North Atlantic Division, said in a statement.

All four soldiers were from 1st Armored Brigade Combat Team, 3rd Infantry Division, based out of Fort Stewart, Georgia.

The division deployed to Europe in January as part of the Pentagon’s bolstering of NATO’s front lines amid Vladimir Putin’s war on Ukraine. The troops were a part of a relatively routine training exercise near Pabradė, a city near the border of Belarus — a key Russian ally.

The identities of the soldiers had not been released Monday. The Army and other military services typically wait to release that information until the next of kin has been notified.

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