The son of former Nazi death camp guard John Demjanjuk has called for an investigation into his father's death at a German nursing home and accused doctors of performing a "medical execution".
"Just before he died unexpectedly, he was given a high dose of a pain killer which is banned in the USA and which the German pharmaceutical manufacturer states should not to be given to patients with his bone marrow condition," John Demjanjuk Jr said in a statement on Wednesday.
"We believe this led to his death and any foul play should be investigated."
German officials said Demjanjuk, who had been convicted of more than 27,000 counts of accessory to murder, appeared to have died of natural causes at the age of 91.
An autopsy gave no clear indication of the exact cause of death but also found no sign that anyone else was involved, a spokesman for the public prosecutor's office in the southern town of Traunstein said several days after Demjanjuk's March 17 death.
Last year a German court sentenced the Ukrainian-born man to five years in prison in connection with the six-month period he was a guard in Poland at the Sobibor death camp in 1943.
Demjanjuk vigorously denied the charges and appealed his conviction, arguing throughout the proceedings that he had been a victim of the Nazis, having been captured by them as a prisoner of war.
He was released pending an appeal, having already spent nearly two years in prison, as he was deemed unlikely to abscond.
After World War II, Demjanjuk went to live in the United States, raising three children there and working in the auto industry. After a legal case brought in Israel in 1986 collapsed, he returned to the United States.
But he was stripped of his citizenship in 2002 for lying about his past and finally deported from the United States to Germany in 2009 to face trial.
His son - who insists Demjanjuk died a scapegoat and a victim - filed a complaint with Bavarian prosecutors asking for an investigation of several doctors and a nurse on suspicion of manslaughter and other charges.
The complaint says that doctors administered a drug called Novalgin which has severe side effects, alleging a "medical execution."
Officials in Germany were not immediately available for comment on Wednesday as their offices had closed for the day.