The chief investigator pursuing Alois Brunner, one of the world's most wanted German Nazi war criminals, has told the BBC that he is "99% sure" that he died four years ago in Syria.
"We cannot prove it forensically, but we are certain that is the case," Nazi-hunter Efraim Zuroff said.
SS captain Brunner, who would now be 102, is accused of deporting more than 128,000 Jews to death camps in WWII.
For many years there has been uncertainty as to whether he is dead.
Dr Zuroff - director of the Simon Wiesenthal Center in Jerusalem - told the BBC that new information had recently come to light about Brunner's death and burial in Damascus from a "reliable" former German secret service agent who had served in the Middle East.
He said that the new evidence revealed that Brunner was buried in an unknown location in Damascus around 2010 and was unrepentant of his crimes.
In April Brunner was removed from the Simon Wiesenthal Center's most wanted list, in a move signifying that it considered him to be dead. Dr Zuroff - who is also a Holocaust historian - said that the latest information provided more concrete evidence to support that conclusion.
"[Brunner] played a key role in the implementation of Hitler's 'Final Solution' to murder Jews," Dr Zuroff said, "and was a monster."
He said that Brunner sent 47,000 Jews in Austria, 44,000 in Greece, 23,500 in France and 14,000 in Slovakia to camps where most were murdered.
In the 1950s Brunner is believed to have fled to Syria. He reportedly later served as an adviser to President Hafez al-Assad and is thought to have instructed his government on torture tactics.
- The Austrian-born SS chief was once described by Adolf Eichmann - the architect of the 'Final Solution' - as one of his best men
- Eichmann dispatched Brunner wherever he felt round-ups of Jews were proceeding too slowly
- From June 1943 until the liberation of France, he sent thousands of Jews to their almost certain deaths
- He waged a reign of terror on the French Riviera, hunting down Jews who had sought refuge in the relative safety of the Italian occupied zone
- It is widely believed that he fled to Syria in the 1950s - living under the false name of Georg Fischer - and that successive regimes offered him protection
- Syria has repeatedly denied harbouring him
In 2001 he was sentenced in absentia to life imprisonment by a court in France.
Brunner was in charge of the Drancy internment camp outside Paris where Jews rounded up in France were held before being sent to the death camps. An estimated 345 children were among his victims.
Dr Zuroff said that Brunner survived at least two Israeli intelligence assassination attempts while in Syria in 1961 and 1980.
He said that the Syrian civil war made it impossible to know the precise location of Brunner's grave.