The search for four U.S. Army soldiers who went missing Tuesday during a training session in Lithuania continued this weekend, officials said.

The soldiers went missing after their M88 Hercules armored vehicle became submerged in a peat bog during the training exercise with Lithuanian armed forces and law enforcement. The vehicle was found more than 16 feet underwater the next day.

The soldiers, who have not been identified, were all from the 1st Brigade, 3rd Infantry Division.

On Saturday morning, more personnel and equipment joined the U.S. and Lithuanian search effort, including specialized divers from the U.S. Navy’s Commander Task Force 68 who arrived from Spain, according to a news release from the U.S. Army, Europe and Africa. Their goal is to find lifting points on the soldiers’ vehicle.

Senior Chief Master Diver Carlos Hernandez, from Underwater Construction Team 1, said the team has touched base with Lithuanian divers who have already been in the bog and have “a good site picture from them.”

“We’re going to start off by putting our Defender [submersible remotely operated vehicle] in the water to paint a clear picture of what we can expect down there, as well as our Artemis Handheld Sonar,” Hernandez said.

Also joining the search Saturday were over 50 Polish engineers and recovery experts, as well as Lithuanian geologists. The specialists brought equipment including four heavy trucks, three WZT-3 tracked recovery vehicles and a man-portable sub-bottom sonar to assist with mapping the area.

“Today’s focus is on continued efforts to remove water and mud from the site, shore up the ground around the site to support heavy equipment, and site preparation for dive operations,” the Army said in the press release.

Multiple helicopters are assisting in the search, including two UH-60M Blackhawks for medical evacuation and three CH-47 Chinooks for heavy lifting, the Army said.