A Citigroup unit and the accounting firm Deloitte & Touche were sued by an investor for helping a mortgage company issue $92.4 million in stock 14 weeks before the lender went bankrupt. The four million shares issued by American Home Mortgage Investment have dropped by 99 percent since they were first offered for sale on April 30 at $23.10 each through Citigroup Global Markets.

Deloitte prepared American Home’s financial reports before the issue. “The offering materials that they issued all omitted information that was material to investors,” Matthew Heffner, an attorney for the shareholder bringing the suit, said Friday.