Olympus hid up to $1.67bn (£1.1bn) of losses from its investors but there is no evidence that organised criminals were involved in the cover-up, an investigation panel is set to report today.
The report into the stricken Japanese giant is also likely to hold back on recommending criminal charges against bosses involved in the scandal.
Instead it will present the facts and leave the camera and medical equipment maker's board to decide on whether to prosecute, Reuters reported from Tokyo.
The report is said to have found that Hisashi Mori, the company's former executive vice-president, and Hideo Yamada, its former internal auditor, led efforts to hide the losses. Olympus has so far admitted it used about $1.3bn of acquisition payments and advice fees to mask losses it made on securities investments.
The panel, which includes a former Supreme Court judge, was appointed by Olympus and has only limited powers to follow trails of money, raising doubts about its ability to pronounce with authority on the affair.
The company is still under investigation by the Tokyo police, prosecutors and Japan's Securities and Exchange Surveillance Commission.
Olympus has lost more than half its market value since the scandal was revealed by its former chief executive Michael Woodford. The English former boss was forced out of the company in October after a matter of weeks at the helm when he raised questions about dubious accounting for the company's acquisitions.
Strong rumours had circulated in Japan that the country's yakuza organised crime rings took part in the cover-up of the false accounting. A favourite tactic of the syndicates is to find out embarrassing information about a company or its leaders and use it to extort payments.
The apparent absence of yakuza involvement could help Olympus in its efforts to avoid being kicked off the Tokyo Stock Exchange. That threatened move would deny it access to equity markets and could force it to sell major assets.
The company has until 14 December to sort out its accounts and report second-quarter earnings but the Tokyo exchange can still force Olympus out depending on the scale of its false accounting or any involvement with organised crime.
The panel found that Messrs Mori and Yamada told the company's former president Tsuyoshi Kikukawa, who at first denied publicly that there was a cover-up but later quit. The company then admitted it had been concealing losses for more than 20 years.
Mr Woodford, who is English and was one of very few foreign bosses in Japan, is trying to oust the current board and return as chief executive with his own team. He is up against Shuichi Takayama, the current Olympus president, who wants to stay on long enough to put the company back on track.