The Justice Department announced it filed a federal complaint Tuesday to revoke the citizenship of an alleged former guard at a Nazi concentration camp during World War II.

The department said it filed the complaint in U.S. District Court in Phoenix to revoke the citizenship of Juris Kauls, of Sun City, Ariz., who the department alleges served as deputy chief and inspector of guards at a concentration camp in the vicinity of Riga, Latvia, now part of the Soviet Union, from September 1941 to December 1942.The department said in a statement that Nazi authorities used the concentration camp to persecute civilian prisoners, including the use of prisoners as slave laborers and "the beating, starvation and execution of prisoners."

In its complaint, the department said, "The guards implemented the daily operation of the camp, disciplined prisoners and carried out acts of persecution."

Kauls, 75, immigrated to the United States in 1954 and became a citizen in April 1960. The department alleged Kauls concealed his involvement with the Nazi concentration camp when he first immigrated to the United States and later when he applied for citizenship.

Neal Sher, director of the department's Office of Special Investigations, said his office's investigations have resulted in the deportation of 19 Nazi persecutors and 28 others have been stripped of their citizenship.

Sher said more than 600 people are under investigation and that other court filings are expected.

Meanwhile, a woman who answered the door at the Kauls' residence and identified herself as Kauls' wife was asked about the allegations.

"That's not possible. We are United States citizens," she said.

She refused to talk further with reporters.

Neighbors said the couple rarely left their home in the retirement community except to go shopping.