Goldman Sachs Group Inc. officials said they knew as far back as August 2008 that regulators were examining controversial mortgage securities created by the firm but were stunned by the bombshell civil fraud suit lodged against it Friday, with most having learned about it from news reports.

Firms typically get a chance to settle such suits, but not in this case, Goldman said. The Wall Street giant said it was alerted to the probe in the summer of 2008 and was warned that it might face a suit in July 2009. It says it then responded in detail to the Securities Exchange Commission's inquiry in September, but heard nothing back from the government until Friday's unveiling of the civil suit. The SEC usually notifies firms ahead of a lawsuit as a courtesy to give them a chance for a last-ditch settlement or to prepare for the public fallout.

The move showed a combative streak from the SEC, which has been under mounting pressure after letting slip through its fingers early probes into the Ponzi scheme of Bernard Madoff and the alleged fraud of Texas financier R. Allen Stanford.

The case, SEC v. Goldman Sachs & Co. and Fabrice Tourre, sets the stage for what could become the signature lawsuit from the financial-crisis era. It comes at a time when the Obama administration is trying to move through Congress a bill to overhaul financial regulations in the wake of the crisis—legislation that would likely affect the regulation of products used in the Goldman deal.

Lawsuits by the SEC are subject to a vote by the agency's five commissioners, and the tally on the Goldman case will be closely watched in Washington, as the current commission is split along party lines—with two Republicans and two Democrats, plus one independent who was appointed by President Obama.