Evidence suggests a prisoner found dead in a high security Israeli prison, whose incarceration has not been acknowledged by the country's justice system or government, was an Australian.
Ben Zygier, know in Israel as Ben Alon, was found dead in a high security hermetically sealed cell specially constructed for the assassin of Israeli prime minister Yitzhak Rabin, the ABC's Foreign Correspondent program has revealed.
Local and international media have speculated that Mr Zygier was the so-called Prisoner X, one of the Israeli security community's most sensitive secrets.
The ABC reports Mr Zygier was initially jailed in the cell and sealed from the outside world in early 2010.
Mr Zygier's arrest and jailing remains a mystery, but the ABC believes he was recruited by Israeli spy agency Mossad.
The Israeli government went to great lengths to keep his identity secret.
It is claimed guards didn't know who they were watching and when reports appeared on an Israeli news website stating that a man was found dead in the Prisoner X cell authorities shut down the site.
Israeli courts have prohibited and publication or public discussion of Prisoner X.
The ABC's Foreign Correspondent reported that Mr Zygier was 34 when he was found dead.
He moved to Israel about 10 years earlier and had married to an Israeli woman and fathered two children.
Seven days after his death, his body was flown to Melbourne where he was buried in Chevra Kadisha Jewish cemetery on December 22.
The ABC sought comment from Mr Zygier's family, friends and acquaintances but all refused to comment.
Foreign Minister Bob Carr said the government had not been informed by Mr Zygier's family or anyone else of his imprisonment.
Mr Carr said the Zygier family would need to contact him if he was to take the matter up with Israel.
He said concerns that Australians were working for Mossad were troubling.
"Australians should not be working, performing intelligence gathering functions for a foreign government using their passport," Mr Carr told the ABC.
"They would have breached, I would guess, half-a-dozen laws by doing that."
Greens leader Christine Milne says she'll encourage Senator Carr to press the Israeli government about the circumstances surrounding Mr Zygier's detention and death.
She said it wasn't enough for the foreign minister to merely say he couldn't do anything because the Zygier family hadn't requested it.
"It is incredible that an Australian citizen, a dual citizen, is alleged to have been held in the manner that was suggested," she told reporters in Canberra on Wednesday.