Securities regulators served subpoenas on a slew of Wall Street firms late last week, specifically seeking information on supervisors of particular analysts and accelerating the second phase of their crackdown on biased research reports. According to sources familiar with the investigation, the Securities and Exchange Commission served the subpoenas on all 10 firms that reached an agreement with the SEC and other regulators in last month's $1.4 billion global settlement. At the time of the settlement, regulators said they would begin taking a hard look at the actions of individual analysts and their supervisors. One securities lawyer who represents several Wall Street analysts said that in recent days, investigators from the NASD, another regulatory agency, have stepped up their interviews of potential witnesses. Even before the latest round of subpoenas went out, it had been known that regulators were particularly focused on pursuing possible civil charges against top supervisors at Citigroup ( C) and Merrill Lynch ( MER). In part, that's because former Citigroup analyst Jack Grubman and former Merrill analyst Henry Blodget are the only two analysts to have reached a settlement with securities regulators in the yearlong probe. In February, for instance, the NASD notified Kevin McCaffrey, Salomon's former director of stock research and a former Grubman supervisor, that it might file charges against him for violating several rules, including failure to supervise an employee and failing to maintain "high standards and honor." He also is being investigated for violating rules on communications with the public. Sources say another supervisor under investigation is Deepak Raj, Merrill's former head of stock research, who resigned from the firm in February after 24 years at the nation's largest brokerage. Raj's lawyer, Betty Santangelo, couldn't be reached for comment. In February, Merrill announced Raj's departure in a memo circulated to its employees. The firm, at the time, called Raj's resignation a "personal" one and an opportunity to explore "new ideas and business opportunities." Officials with a number of Wall Street firms, including Merrill Lynch, Citigroup and J.P. Morgan Chase ( JPM), declined to comment.