Mr. Plumb of Security Trust acknowledged in his client letter that the company was facing a severe challenge.

A representative of Security Trust said he could not comment because he had not seen the regulators' filings.

In the mid-1980s, he worked for Selective Security Trust of America.

Security Trust and its top executives disguised the trades in a variety of ways to conceal the trading from the mutual funds.

Security Trust arranged for Canary to engage in late trading in Bank One's funds, the complaint said.

A number of the trades were processed through Security Trust, an intermediary in the processing of mutual fund trades by pension plans.

The case could increase the turmoil within the fund industry and among 401(k) plans and other retirement accounts served by intermediaries like Security Trust.

A spokeswoman for Security Trust, Nancy Murphy, said last night that she "could not speak to" the likelihood of criminal charges against the company.

Besides its impact on the fund industry, a criminal complaint against Security Trust could raise the stakes for state and federal regulators.

Security Trust has overhauled its management team in the last six weeks, Ms. Murphy said.