Four U.S. Army soldiers who went missing during a scheduled tactical training mission in Lithuania on Tuesday have reportedly died, according to NATO Secretary General Mark Rutte. The soldiers—who have yet to be identified publicly—were in a training area commonly used tactical military exercises near the city of Pabradè. The U.S. military announced Wednesday that recovery efforts were underway for the soldiers and their vehicle, which, according to military officials, might have become submerged in a swamp. (Per the Associated Press, a U.S. official confirmed only that the soldiers had been involved in a “training incident,” without confirming fatalities.) Lithuanian law enforcement and the Lithuanian Armed Forces have been aiding in the search. In a statement Wednesday, Lt. Gen. Charles Costanza, thanked the first responders: “It’s this kind of teamwork and support that exemplifies the importance of our partnership and our humanity regardless of what flags we wear on our shoulders,” he said.