Investigations into scandal-hit Olympus Corp revealed an elaborate scheme for concealing losses on risky bets behind a facade of inflated bank deposits and securities holdings, The Nikkei reported.

At its peak at the end of March 2005, this wall of assets, which hid impaired securities investments dating back to the 1990s, stood at more than 130 billion yen ($1.68 billion), according to details revealed in an ongoing investigation by a third-party committee, the business daily said.

Sources say Olympus moved the impaired securities off its books -- a trick known in Japanese as tobashi -- to prevent the painful write-downs that would have followed the introduction of fair value accounting in fiscal 2000, Nikkei said.

The third-party committee conducting the investigation said it will report its findings early next month. Olympus is waiting for these findings before it reports first-half earnings and issue second-quarter financial statements, the daily reported.

On Thursday Tokyo's stock exchange has warned Olympus it will be delisted if it fails to report earnings by December 14, deepening concerns about the camera-maker's future.

The 92-year-old company's shares started falling in October after sacked chief executive Michael Woodford went public with assertions Olympus had improperly accounted for $1.5 billion in payments related to mergers and acquisitions.

Olympus denied wrongdoing after Woodford turned whistleblower, but stunned investors on Tuesday by revealing it had used M&A deals to hide securities investment losses. ($1 = 77.520 Japanese Yen)

(Reporting by Soham Chatterjee in Bangalore; Editing by Supriya Kurane)