Yakuza crime syndicates could be involved in the multibillion dollar cover-up.

Tokyo police unit that targets organised crime has joined the investigation into the Olympus scandal, over fears that Yakuza crime syndicates could be involved in the multibillion dollar cover-up.

The involvement of the specialist division of the Tokyo Metropolitan Police emerged yesterday. However, a source told Reuters that it was too early to say whether gangsters were involved in the case.

Olympus admitted this month that it had been using payments relating to a series of transactions to cover up losses at the group, adding that the practice had stretched back over two decades.

Speculation over the involvement of organised criminals has grown since the turmoil at the company was revealed. Yet the police investigation is the first official acknowledgement that Yakuza syndicates may be involved in the scandal.

The news comes as a former board member of the precision equipment maker demanded the re-instatement of its sacked chief executive, Michael Woodford.

Koji Miyata, who was on the board of Olympus between 1995 and 2006, told the company to apologise to Mr Woodford after he was fired for raising "serious governance concerns" over four transactions.

He told the Associated Press: "No matter how you look at this, the only person who did the right thing all along was him." Mr Miyata has launched an online petition calling for the company to re-appoint Mr Woodford as the chief