Shares in Japan's disgraced Olympus Corp surged on Tuesday as investors bet that a probe into its scandal-ridden accounts would not turn up any nasty new surprises which could lead to the stock being delisted.

An outside investigative panel, which has spent the past month trying to get to the bottom of one of Japan's worst accounting scandals, is due to present its findings at 0600 GMT on Tuesday, though the report could be released before then.

Olympus, a maker of cameras and medical equipment, has lost half its market value since its sacked CEO, Englishman Michael Woodford, went public in mid-October with concerns over murky accounting and some expensive and questionable acquisitions.

But the stock jumped as much as 15 percent on Tuesday, extending a three-week rally fuelled by growing hopes that Olympus would not be delisted and that, instead, a few former executives would bear the brunt of any punishment.

I think the probability for Olympus to be kept as a listed company is pretty high right now and that is the market consensus right now, said analyst Nanako Imazu of CLSA.

Olympus must clear a series of hurdles to avoid being delisted, a humiliation that could force it into asset sales. The first of these challenges would be met if the panel were to find no involvement of organised crime in the scandal.

A source familiar with the panel's inquiries has told Reuters that the investigators, led by a former supreme court judge, have found no evidence to support a much-rumoured link with organised crime or yakuza gangsters.

The panel, a group of experts formed by Olympus in early November, has also found that Olympus hid up to $1.67 billion (1.07 billion pounds) in losses from its investors in an accounting cover-up that stretched as far back as the 1990s, and that two former executives led the concealment, the source has said.

If confirmed on Tuesday, this would not represent a major new surprise for investors, with Olympus having already admitted to hiding substantial investment losses for two decades and having named three former executives as the main wrongdoers.

JOINT INVESTIGATION WITH POLICE

Some doubts exist, however, about the ability of the panel to get to the bottom of such a complex and murky affair, which involves numerous, obscure counterparties and investment firms.

The panel has limited powers of investigation and was hired by the same board that sacked Woodford, who blew the whistle on the scandal immediately after he was fired as CEO in October.

I would have thought they didn't have the expertise to probe that (involvement by organised crime), said Jamie Allen, secretary-general of the Asian Corporate Governance Association, whose members include institutional investors that collectively manage assets of more than $10 trillion.

That's really a job for the police. So even if they say there's no evidence, obviously I don't think that's going to satisfy everybody because they'll want to know what the police come up with.

Olympus remains under joint investigation by Japanese police, prosecutors and the markets regulator, though it is not clear when these official investigations will wind up.

Even if neither the panel nor the official investigations find evidence of involvement by organised crime, Olympus still needs to meet a December 14 deadline to iron out its accounts and report its second-quarter results in order to remain listed.

Olympus plans to meet with its creditor banks, which have so far been supportive, as early as December 16 to explain its situation, Kyodo news agency said.

Compounding the current board's problems, Woodford has mounted a campaign to oust all of the current directors and replace them with his own team of candidates with himself in charge of the boardroom as nominated CEO.

The panel is expected to find that two men, former executive vice president Hisashi Mori and ex-internal auditor Hideo Yamada, led the extensive cover-up of losses.

The Nikkei newspaper said on Tuesday that two ex-presidents, Tsuyoshi Kikukawa, who served from 2001 until the scandal broke, and his predecessor, Masatoshi Kishimoto, were both thought by the panel to have been made aware of the accounting tricks.

Kishimoto, who held office from 1993 to 2001, told the committee he knew nothing about the cover-up, while Kikukawa said he found out about the losses only recently, the Nikkei said, quoting sources familiar with the investigation.

The Olympus board will meet on Wednesday to discuss its next steps, once investors have had time to digest the panel's findings, the daily said.

Olympus shares trimmed their early gains before the end of the morning session, but were still up nearly 9 percent.

(Additional reporting by Mari Saito in Tokyo; Writing by Mark Bendeich; Editing by Richard Pullin)