They join a growing number of Western military volunteers captured by Russian forces, including at least two British.
Aiden Aslin and Shaun Pinner have already been told they face the death penalty as “mercenaries.”
The capture of the two Americans will be diplomatically sensitive, as the Kremlin may try to use it as proof that America is directly involved in the war. Russian President Vladimir Putin is likely to demand major concessions to release them.
A colleague of the two men, who asked not to be named, told The Telegraph that they had been captured after encountering a much larger Russian force during a battle last Thursday.
“We were on a mission and everything went crazy, with bad intelligence,” he said. “We were told that the city was clear when it turned out that the Russians were already attacking it.
“They went down the road with two T72 tanks and multiple BMP3 (armored combat vehicles) and about 100 children. The only one there was our 10-man team.”
The team set up defensive positions, during which time Drueke and Huynh fired a rocket-propelled grenade at a Russian vehicle, destroying it.
This, however, caught the attention of one of the tanks, which fired in its direction but is believed to have failed.
Shortly afterwards, the tank was stopped by an anti-tank mine that the Ukrainian squadron had left on the road. The two Americans then disappeared into the fog of battle and are believed to have been captured by Russian infantry.