Federal authorities have begun deportation proceedings against a retired welder they contend was an Auschwitz concentration camp guard and moved to revoke the citizenship of an alleged member of a World War II police unit that persecuted Jews and civilians.

The Justice Department said Albert Ensin, 65, was a guard at Auschwitz between December 1941 and July 1943.

Ensin, a Lithuanian native who is not a U.S. citizen and lives in Stoughton, Mass., south of Boston, plans to fight the deportation attempt on grounds he never participated in the persecutions at the camp and that the Justice Department was assisted in its investigation by the Soviet Union, his lawyer said.

In a separate case, a complaint filed in U.S. District Court in Syracuse, N.Y., said that for six months in 1941 Mikelis Kirsteins was a member of the Latvian Security Auxiliary Police, published reports said Thursday.

That group, also known as the Arajs Kommandos, is reported to have killed Jews and other civilians in Latvia.

Kirsteins collapsed Thursday with an unspecified heart problem and was listed in critical condition at St. Luke's Memorial Hospital in Utica, N.Y.

Kirsteins, a retiree who lives near Utica, is a Soviet native who immigrated to the United States in 1956 and became a citizen in 1965. The Justice Department said Kirsteins did not disclose his involvement with the Kommandos or the persecution, which would have made him ineligible to enter the United States.

The department will not file criminal charges, and Kirsteins can challenge the complaint at a hearing in U.S. District Court, according to Joseph Krovinsky, a spokesman for the Justice Department.

If the department wins its case, Kirsteins would face possible deportation to the Soviet Union.