Earlier this month, it was revealed that Lehman Brothers had managed to keep $50 billion worth of debt from its balance sheet using the process, which was described as an "accounting gimmick" by the court-appointed examiner hired to look into the failure of the firm.
More than 20 organisations have now been asked by the SEC whether they have also employed the practice, which works by filing temporary repurchase agreements as permanent asset sales, during the past three years.
Mary Schapiro, chairman of the SEC, told CNBC: "We are looking at the Lehman activity very, very carefully and all the issues surrounding Repo 105."
Earlier this month, Merrill Lynch insiders told the Financial Times that they had warned the SEC about Lehman Brothers' dubious accounting practices as early as March 2008.
By Claire Archer