Olympus Corp. shareholders, including Nippon Life Insurance Co., lost more than ¥250 billion in value of their holdings in the first two trading sessions after the board fired President Michael C. Woodford.

The maker of cameras and medical equipment plunged 24 percent, the most since at least September 1974, to ¥1,555 at the close of trading Monday on the Tokyo Stock Exchange. The stock fell 18 percent Friday after the ouster of Woodford was reported.

Goldman Sachs Group Inc., Deutsche Bank AG and Nomura Securities Co. slashed their stock ratings amid concerns about the company's corporate governance and costs. Olympus may face regulatory and legal scrutiny because of payments made to advisers in a 2008 transaction, according to a PricewaterhouseCoopers LLC report commissioned by Woodford.

"There seems to have been funny business going on," said Edwin Merner, president of Atlantis Investment Co. in Tokyo. "Maybe Olympus can be turned around by a new management. We will have to wait and see."

Olympus was valued at ¥422 billion as of Monday, down from the ¥673 billion at the close of trading on Thursday, the day before Woodford was fired.

Nippon Life, the largest shareholder in Olympus, lost about ¥21 billion in the value of its holdings, based on Bloomberg's calculation of the 22 million shares held by the company. The insurer owned 8.3 percent of Olympus, according to data compiled by Bloomberg.

Olympus spokesman Seisho Tanaka wouldn't comment on statements from Woodford or the PricewaterhouseCoopers report. Akira Tsuzuki, a spokesman for Osaka-based Nippon Life, Japan's biggest life insurer, also declined comment.

Potential offenses include false accounting, financial assistance and breaches of duties by the board, according to the Oct. 11 report that Woodford gave to Bloomberg News.

Olympus is considering measures, including legal action, against Woodford for leaking internal information to the media, Executive Vice President Hisashi Mori reportedly said Monday.