WASHINGTON (CNN) -- The Justice Department has revoked the U.S. citizenship of a 73-year-old former Nazi concentration camp guard living in Connecticut and is moving to deport a Chicago-area man who allegedly guarded Jewish prisoners in Lithuania.

Walter Berezowskyj, a retired steel plant machine operator who came to the United States in 1949, admitted to violating immigration laws and agreed to relinquish his citizenship and accept deportation. However, the government agreed not to deport Berezowskyj unless his "rapidly deteriorating mental condition" improves.

The U.S. government accused Berezowskyj of training at an SS facility in Poland in 1943 and of serving as an armed guard at a labor camp called Poniatowa. In November 1943, all of the prisoners alive at Poniatowa were shot to death. Subsequently, Berezowskyj was a guard at Mauthausen, an Austrian camp where prisoners were murdered.

On Monday, the Justice Department filed a complaint in U.S. Immigration Court in Chicago seeking the deportation of Vincas Valkavickas, 78, a retired factory worker.

The complaint says that Valkavickas was a Lithuanian police officer from 1941 to 1944, helping Nazi forces guard Jews at a former military installation near Sviencionys.

Since the Justice Department's Office of Special Investigations was formed in 1978 to ferret out alleged Nazi collaborators living in the United States, 48 people have been removed and another 300 people are under investigation.