U.S. securities regulators subpoenaed firms including Deutsche Bank, Goldman Sachs and Merrill Lynch as it probes suspected manipulation of Lehman Brothers and Bear Stearns shares, Bloomberg said, citing two people familiar with the matter.

The U.S. Securities and Exchange Commission is seeking trading records and e-mails, one of the people told the news service.

The SEC has sent subpoenas to more than 50 hedge-fund advisers, seeking trading and communications data related to short-selling and options trading in Bear Stearns or Lehman Brothers, The Wall Street Journal said on Tuesday, citing a person familiar with the matter.

Rumours have been blamed for the collapse of investment bank Bear Stearns and for the significant slide in Lehman shares this month.

With financial stocks dropping dramatically over the year, lawmakers have been calling on the SEC to investigate whether short sellers and speculators are behind the move.

Over the weekend, the SEC announced plans to crack down on false rumours and said it was examining whether broker dealers and investment advisers had controls in place to prevent market manipulation.