Germany is investigating an alleged former Auschwitz death camp guard, prosecutors said Wednesday, who according to media reports is listed among the Simon Wiesenthal Center's most-wanted Nazis.

Prosecutors in the southwestern city of Stuttgart confirmed to AFP they had "started investigating an alleged concentration camp guard in autumn of 2012" and that he had worked in Auschwitz.

They declined to name the suspect and said no charges had been laid.

But German media identified him as Hans Lipschis, aged 93 and living in the town of Aalen in the southwestern state of Baden-Wuerttemberg. He says he worked as a cook, not a guard, in the camp in occupied Poland, public broadcaster SWR reported late Tuesday.

Lithuanian-born Lipschis was granted "ethnic German" status by the Nazis. He moved to the United States in 1956 but was deported to Germany in 1983, Welt am Sonntag newspaper reported last weekend.

The Simon Wiesenthal Center in its 2013 report lists him as its fourth most-wanted Nazi, saying he served in the SS-Totenkopf Sturmbann (Death's Head Battalion) from 1941 until 1945 at Auschwitz and "participated in the mass murder and persecution of innocent civilians, primarily Jews."

More than one million people were murdered in Auschwitz-Birkenau during World War II.

Germany has broadened the scope of its pursuit of Nazi war criminals since the 2011 conviction of Ukraine-born John Demjanjuk, a former guard at the Sobibor death camp in Poland.

In that case, the court ruled that any role at a death camp amounted to accessory to murder, widening culpability from those found to have personally ordered or committed murders and atrocities.

Demjanjuk was sentenced to five years' prison for complicity in 28,000 murders. He died last year while free awaiting an appeal.

Lipschis is among 50 surviving Auschwitz staff who are being investigated in Germany under the broadened culpability rules.