Last Updated 10:26 a.m. ET
(CBS/AP) BERLIN - German police say John Demjanjuk, who was convicted last year of serving as a Nazi death camp guard, has died.
Rosenheim police official Kilian Steger told The Associated Press that the 91-year-old died Saturday at a home for the elderly in southern Germany where he has stayed since his trial ended in Munich last year.
Steger says prosecutors in nearby Traunstein are looking into the case as a routine procedure.
Demjanjuk, a retired Ohio autoworker, was deported to Germany in 2009 to face trial in Munich after being stripped of his U.S. citizenship.
His son, John Demjanjuk Jr., told the Associated Press in a telephone interview from Ohio that his father died of natural causes. Demjanjuk had terminal bone marrow disease, chronic kidney disease and other ailments.
It was not yet known whether he would be brought back to the U.S. for burial.
Demjanjuk was convicted in May 2011 of thousands of counts of acting as an accessory to murder at the Sobibor camp in Nazi-occupied Poland. He was charged with 28,060 counts of being an accessory to murder, one for each person who died during the time he was accused of being a guard.
There was no evidence he committed a specific crime. The prosecution was based on the theory that if Demjanjuk was at the camp, he was a participant in the killing - the first time such a legal argument has been made in German courts.
Demjanjuk was sentenced to five years in prison, but was released pending appeal.
Last December a federal judge in Ohio.
The Ukrainian-born Demjanjuk had steadfastly denied any involvement in the Nazi Holocaust since the first accusations were levied against him more than 30 years ago.
"My father fell asleep with the Lord as a victim and survivor of Soviet and German brutality since childhood," Demjanjuk Jr. said. "He loved life, family and humanity. History will show Germany used him as a scapegoat to blame helpless Ukrainian POWs for the deeds of Nazi Germans."
Presiding Judge Ralph Alt said the evidence showed Demjanjuk was a piece of the Nazis' "machinery of destruction."
"The court is convinced that the defendant ... served as a guard at Sobibor" from March 27, 1943, until mid-September 1943, Alt said in his ruling.
Israeli Holocaust scholar Yehuda Bauer, who researches at the Yad Vashem memorial, said Demjanjuk's story showed an important moral lesson.
"You don't let people, even if they were only junior staff, get away from responsibility," Bauer said.
Despite his conviction, his family never gave up its battle to have his U.S. citizenship reinstated so that he could live out his final days nearby them in the Cleveland area. One of their main arguments was that the defense had never seen a 1985 FBI document, uncovered in early 2011 by The Associated Press, calling into question the authenticity of a Nazi ID card used against him.
Demjanjuk maintained that he was a victim of the Nazis himself first wounded as a Soviet soldier fighting German forces, then captured and held as a prisoner of war under brutal conditions.
"I am again and again an innocent victim of the Germans," he told the panel of Munich state court judges during his 18-month trial, in a statement he signed and that was read aloud by his attorney Ulrich Busch.