A committee investigating disgraced Japanese electronics manufacturer Olympus has blamed the company's “rotten” top management and “contaminated” senior executives for the accounting scandal that has rocked the company.

The panel's report Tuesday said that a small circle of senior officials was responsible for the elaborate plot to use a series of suspicious business deals to disguise financial losses on securities investments of up to $1.73 billion dating back to the 1990s.

But committee chairman Tatsuo Kainaka said there was no evidence to support the media-fueled rumors that Japan's “yakuza” gangsters were involved in the cover-up.

The committee also praised the company's former CEO Michael Woodford, who was fired in October after bringing the scandal to light.

Although the report contained no major unexpected findings, the camera and medical equipment maker still faces possible de-listing from the Tokyo Stock Exchange if it does not submit its revised earnings report by December 14.

The panel identified former vice president Hisashi Mori and ex-internal auditor Hideo Yamada as central figures behind the scheme. Both have since resigned.

Kainaka said other board members were aware of the scheme, but he said the company as a whole did not participate in the cover-up.

Olympus originally denied wrongdoing in the case, but then acknowledged that massive losses were hidden in part through a $2 billion purchase of a British medical equipment maker in 2008. The purchase price included a $687 million advisory fee, which was far above the usual fee paid for such a deal.

Another $773 million in losses was hidden through the purchases of three small Japanese companies between 2006 and 2008. The companies had little to no relation to Olympus' core operations.

The 92-year-old company is still under investigation by Japanese police and public prosecutors, who may bring criminal charges against senior officials.