The sacked chief executive of Japan's disgraced Olympus Corp says he has accepted an invitation to attend the company's board meeting this week, which could be a hopeful sign for investors who want him to return and lead a clean-up of the firm.

Olympus shares jumped 20 percent to 869 yen on Tuesday as traders speculated the company might avoid being delisted from the Tokyo Stock Exchange, despite being engulfed in an accounting scandal.

Olympus, a maker of cameras and medical equipment, is under investigation by regulators, prosecutors and organized-crime police. The scandal broke when CEO-turned-whistleblower Michael Woodford publicly questioned the company's accounts after being fired last month.

I was invited to the board meeting on Friday by Olympus and welcome the opportunity of going to Japan, Woodford, a Briton, told Reuters in London on the eve of his departure for Tokyo.

The trip will be his first to Olympus headquarters since his sacking at a board meeting just over five weeks ago.

Woodford has been cast by two major foreign shareholders as the best man to lead a clean-up of the 92-year-old company, which has lost about 65 percent of its market value since he went public with his concerns about improper accounting.

Goldman Sachs is now the second-biggest shareholder in Olympus, a public filing showed on Tuesday. The Wall Street bank has a 6.67 percent stake, second in size to Mitsubishi UFJ Financial Group's 7.61 percent holding.

Goldman spokesman Michael DuVally said the bank bought Olympus shares from clients in the normal course of business as a market maker and was not making a strategic investment.

Other big players, such as Morgan Stanley, also appear to have been buying up the stock on behalf of clients, market sources said.

Olympus, which at first denied any wrongdoing, this month admitted to hiding investment losses from investors for two decades and to using some of $1.3 billion in unusual merger and acquisition payments to help in the cover-up.

It was not immediately clear whether the man who presided over Woodford's sacking, former chairman and president Tsuyoshi Kikukawa, would also attend the board meeting. Kikukawa quit as chairman over the scandal last month but remains a director.

Speculation about organized-crime links has swirled around the Olympus scandal, but the firm said on Monday that a third-party panel it set up to investigate the matter had, so far, found no evidence that funds from its M&A deals went to organized crime syndicates or that yakuza gangsters were involved.

The panel's report is due in early December.

Woodford has cited unspecified security concerns for his decision to leave Japan in a hurry after he was sacked. But he said on Monday he was comfortable about returning and reiterated his willingness to go back and run the company.

I'm reassured about the security. The Japanese authorities are aware and arrangements have been made that I'm satisfied with, the 31-year Olympus veteran said.

Woodford, who remains a director, would not discuss the agenda of the board meeting, saying only that it would be an opportunity to ask my colleagues to do the best for Olympus.

During his visit this week, Woodford will meet Japanese police and other authorities, he has said.

SPECULATION OVER ORGANISED CRIME

The scandal at the once-proud firm has rekindled concerns about lax corporate governance in Japan and revived worries about links between companies and organized crime.

A unit from the Tokyo Metropolitan Police Department's organized crime division has joined the investigation, a source familiar with the matter said on Friday. But the source added it was premature to say if gangsters were involved.

Speculators who believe Olympus' core medical equipment business still has value have been betting that executives responsible for the scandal will bear the brunt of any punishment and that the company can escape with a fine.

Olympus has admitted to improperly accounting for M&A payments going back to 2006. A large share of these payments went to obscure Cayman Islands companies that have since closed, making it difficult to trace the money.

Tokyo prosecutors have already questioned former vice-president Hisashi Mori on a voluntary basis, Japanese media say, and are expected to soon question Kikukawa and internal auditor Hideo Yamada.

Olympus' new president, Shuichi Takayama, has blamed the three for the cover-up, saying he would consider criminal complaints against them.

Mori was sacked as an executive this month but, like Kikukawa, he remains a director.

It is unclear whether Mori will attend this week's board meeting.

The Tokyo exchange has placed Olympus on a watch-list as a possible prelude to delisting. If the firm misses a December 14 deadline for filing its financial statements for the six months to September, it will be automatically delisted.

Even if Olympus meets the deadline, the bourse can still delist the stock depending on the scale of its past financial misstatements or if the firm is found to have done business with organized crime syndicates.