Speculations were made in Australia regarding some foul play as the prisoner was said to have committed suicide in a cell equipped with sensitive surveillance system to prevent any such attempt and was specially made for the assassin of former Israeli Premier Yitzhak Rabin.
The Israeli government however maintained a studied silence up until now even though Deputy Prime Minister Moshe Yaalon yesterday in a TV programme insisted that Israel abided fully by the law, even in the case of security prisoners.
Zygier, who immigrated to Israel in around 2001 and at some point joined Mossad after serving in Israel Defence Forces, is understood to have been arrested in February, 2010, on charges which remain subjected to a tight gag order.
Three months later, Israel's most popular news portal, Ynet, briefly ran a report about a prisoner held in top secret conditions whose identity and alleged crime were not known even to his jailers, but it was quickly taken offline under a gag order.
Zygier was found hanged in his cell in December, 2010, a day after he met a leading attorney who has told the local media that he could see no signs of physical or psychological distress.