The Enron probe is widening. According to lawyers for Enron shareholders say that they intend to expand their lawsuits to include other big Wall Street firms, such Merrill Lynch, Salomon Smith Barney’s parent company, Citigroup, and JP Morgan Chase. The suit, which has class-action status, will be amended to include those firms on April 8th, sources say.

The firms declined to comment on the case.

According to a Houston attorney familiar with the Enron case, the suit will allege that Merrill promoted sales of Enron stock as the company was misstating its income and debt. But to win, Enron shareholders’ lawyers will have to prove that Merrill knew about the fraudulent bookkeeping and deliberately mislead them. For example, the suit also alleges that Smith Barney’s parent, Citigroup, acquired detailed knowledge and insight of Enron's finances as lenders and vendors of financial services. .

Plaintiffs will have to show there was a direct pipeline between Merrill, Citigroup and other firms that shareholders relied on, the attorney says.

The suit comes on the heels of UBS PaineWebber being sued by two clients of Chung Wu, the broker who was fired by the firm after e-mailing clients advising them to sell their Enron shares.

Industry attorneys, as well as brokers nationally, have predicted that the Enron collapse is going to hit many Wall Street wirehouses in a variety of ways—and Merrill and Smith Barney appear to be the latest companies to be whacked. Enron had many ties to Wall Street. Many firms underwrote Enron share offering, sold Enron debt or marketed Enron limited partnerships. Nearly every analyst on the Street had a buy on Enron shares at one time or another.