The federal investigation into Bernard L. Madoff’s $65 billion Ponzi scheme widened Wednesday with the arrest of an accountant who had audited Mr. Madoff’s investment advisory business for more than a decade.

David G. Friehling, who operated from a tiny storefront office in the New York City suburb of New City in Rockland County, was charged with securities fraud and with aiding the investment adviser fraud committed by Mr. Madoff. A related civil case was filed against him and his firm, Friehling & Horowitz, by the Securities and Exchange Commission.

But while the new cases shed some light on how Mr. Madoff covered up his fraud for so long, they do not clarify how long ago the fraud began.

Mr. Friehling, who surrendered at the federal courthouse in Manhattan on Wednesday morning and was released on bail in the afternoon, became Mr. Madoff’s primary auditor in the early 1990s when his father-in-law and partner, Jeremy Horowitz, retired and he took over the two-man firm.