TOKYO — More than two months after Olympus’s former president blew the whistle on a huge accounting fraud, the Japanese authorities raided the company’s headquarters here Wednesday, emerging several hours later with boxes full of documents.

TV camera crews were in position outside the building for the raid by investigators wearing dark business suits. But it will probably take more than symbolic action at this point to assure investors that meaningful action will be taken to address a scandal that has caused Olympus’s stock-market value to plunge since early October.

Top Olympus executives admitted last month to covering up $1.7 billion in past investment losses in a global scheme that has led to public investigations on three continents. Olympus came clean on some losses in five years’ worth of revised statements last week, which showed shareholders’ equity plunging to just ¥42.9 billion, or $550 million, and casting a shadow over its long-term viability.

Three executives implicated in the cover-up have left the company. Still, the rest of the Olympus board has been scrambling to retain control of the company with the backing of Japan’s biggest banks, which hold great sway over top corporations, serving as both top lenders and as major shareholders.

The Sumitomo Mitsui Financial Group is the biggest lender to Olympus, with ¥227.5 billion in outstanding loans and bonds, according to Reuters, and also holds a 3.4 percent equity stake in the company. Olympus’s other main lender-cum-shareholder, Mitsubishi UFJ Financial Group, has also stood by the company’s management.

Together, they are likely to bring in a new domestic investor to inject more capital into the company, diluting the influence of foreign investors and their role in shaping the company’s future, according to several people with knowledge of the plans. That has caused dismay among foreign shareholders, who say the current management is tainted and should go for the sake of robust corporate governance.

In fact, foreign investors say that the reaction to the scandal is shaping up to confirm their worst fears about Japan Inc.: that entrenched executives — with the help of friendly bankers and staid institutional investors — will thwart any attempts at much-needed overhaul. Sumitomo Mitsui Financial and Mitsubishi UFJ Financial declined to comment Wednesday.

The eventual Olympus bailout could even be a Japan-wide effort: earlier this week, the Nikkei business daily reported that Olympus might issue about ¥100 billion in new preferred shares, and that Japanese technology companies like Fujifilm or Sony could be possible buyers. The two companies denied that any such investment was in the works.

The U.S. fund manager Southeastern Asset Management, a supporter of Michael C. Woodford, the company’s ousted chief executive, and a big foreign shareholder with a stake of about 5 percent in Olympus, has urged Olympus not to go ahead with any fund-raising plans until a new board is put in place.

Any moves by Olympus to inject new equity into the company would also shut down efforts by Mr. Woodford to return to the company’s helm with a new slate of directors. Mr. Woodford, a British national and one of a handful of foreign executives to have led a top Japanese corporation, was fired in mid-October after he quizzed the Olympus board over a series of outsize acquisition payments that were later found to be part of the company’s loss cover-up.

Mr. Woodford has said he has enlisted “impressive” members of the Japanese business community to join his would-be board and has outlined his own plans to raise capital, either through private equity or a rights issue.

But working with private equity firms, especially from overseas, may not go down well with Japanese investors, who often see them as vulture funds looking to feast on weak Japanese companies and sell off their assets piecemeal.

But Mr. Woodford argued that accepting help from a rival like Fujifilm or Sony would be an even more perilous way forward for Olympus. “What would their motivation be?” Mr. Woodford said. “An investment could eventually move toward a takeover of Olympus, of Olympus giving up independence.”

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