The conman wore a silicone mask of minister Yves Le Drian and conduct a video chat.

French investigators are probing whether a conman who became known as the "Fake Chairman" for scamming banks out of millions of dollars by posing as a top-ranking executive gave himself a promotion - to government minister.

Gilbert Chikli, a 53-year-old French-Israeli citizen, is at the center of an investigation into a caper that may have netted some $90 million by convincing heads-of-state, clergy, business figures, large charities and other luminaries that they were working with France's defense minister to free French citizens kidnapped by Islamists in the Middle East and Africa, according to the BBC.

The alleged ruse was as outlandish as it was elaborate: According to French prosecutors, Chikli or someone else in his crew would don a custom-made silicone mask of France's then defense minister Jean-Yves Le Drian and sit behind an impressive desk in a room decorated to look like a ministerial office, complete with a large French flag and a portrait of the nation's president, and conduct a video-chat with the target of the scam.

Le Drian, now France's foreign minister, has conceded that the con was "impressive" noting that the scammers did a good job impersonating him. But to investigators in France and Israel, the case has been an embarrassing breach of national security.

"This is not an ordinary case but one with great international sensitivities that has caused a diplomatic incident between our two countries. This case is being investigated around the clock in both Israel and France," a member of Israel's fraud police told a judge after the arrests of three Israeli citizens in March, according to the Times of Israel.

The scheme typically involved a purported aide to Le Drian making contact with the mark to set up a Skype video call with the minister himself to discuss an issue of urgent priority that required the utmost discretion: raising funds to secure the release of French citizens being held by terrorists.

France, as a matter of policy, does not pay ransoms to free its citizens and the scammers claimed that in order to keep the payments quiet, the money must be sent to bank accounts in Hong Kong.

Some of those who were contacted in the swindle told a French documentary series that the Skype calls were made to be short, with a poor Internet connection being blamed for the brevity. The room was poorly lit and the Le Drian imposter was kept a good distance from the camera.

"Everything about the story is exceptional," said Delphine Meillet, a lawyer for Le Drian told the BBC. "They dared to take on the identity of a serving French minister. Then they called up CEOs and heads of government round the world and asked for vast amounts of money. The nerve of it!"

According to Meillet, a Turkish businessman accounted for half of the $90 million stolen while the Aga Khan was taken for more than $20 million.

But for all the attention to detail, the trickery partly fell apart over a simple social nuance.

During one of the calls from the bogus Le Drian with Senegal President Macky Sall, the imposter addressed Sall with the formal "vous." In fact, the two know each other well and the real Le Drian would have used the more informal and familiar "tu" with Sall, the BBC reported.

The suspects arrested in Israel have denied involvement in the scam and are awaiting trial in Israel. But the case has once again focused attention on Chikli, who shot to fame in 2015 when he was convicted in France for impersonating bank CEOs to steal some $9 million from 33 institutions. He is currently in prison in France after being extradited from the Ukraine in 2017. He had hid in Israel following his 2015 indictment.

Chikli's exploits as the "Fake Chairman" inspired a poorly reviewed film called "Thank You For Calling" and he appeared to relish his notoriety while on the run, posting videos taunting French authorities online.

Whether he is linked to the Le Drian deception remains unclear, but investigators are looking into whether he masterminded the plan and recruited a crew to carry it out even after his apprehension.

According to the BBC, Chikli had tried to impersonate Le Drian by drafting up a contract in the minister's name to trick the Tunisian government to pay millions for Tiger helicopters they never actually ordered.