New York's attorney general says he is launching an investigation into whether some traders used illegal tactics to drive down the stock price of several Wall Street firms.

Attorney General Andrew Cuomo told reporters Thursday his office has received a "significant number" of complaints about short sellers, or investors who hope to profit by placing bets that a company's stock will fall.

Short-selling is not illegal. But Cuomo says he will focus on whether short sellers engaged in conspiracy or spread bad information to influence the stock prices of Lehman Brothers Holdings Inc., American International Group Inc. and other firms that have been hammered in the ongoing financial crisis.