VIENNA, JUNE 3 -- Martin Bartesch, a former Nazi concentration camp guard who was deported from the United States last week, is still a U.S. citizen and will be sent back there as an undesirable alien, Austrian officials said today.

U.S. Ambassador Ronald Lauder was summoned to the Interior Ministry and informed of the government's decision. Lauder was told that under Austrian law, Bartesch is considered a U.S. citizen because he carries a valid U.S. passport.

The Romanian-born Bartesch, 60, was detained Monday while visiting his family near Linz in western Austria, and held in custody pending deportation.

The former Nazi SS trooper is accused of having murdered a concentration camp inmate when he was a guard at Mauthausen camp, near Linz, during the final years of World War II.

Bartesch arrived here in late May on a U.S. passport after learning that a federal court in Chicago would be asked by the Justice Department to deport him. Shortly after his arrival here, he lost his U.S. citizenship. Before leaving the United States, Bartesch had said that he planned to settle in Austria.

After the war, Bartesch lived in Austria until 1955, when he emigrated to the United States. He was granted U.S. citizenship in 1966, but did not disclose his Nazi past, according to the Justice Department.

{Bartesch's son said earlier this week that his father had admitted in a sealed agreement with Justice that he misrepresented his presence at Mauthausen in his immigration application.}