(updated to reflect sourcing to Bloomberg News) The Securities and Exchange Commission has ramped up its investigation into a range of potentially illegal activity tied to the nation's mortgage meltdown, according to a published report Monday. SEC probes tied to subprime lending and related mortgage banking activity have risen 40 percent since January, Bloomberg News reported, citing a source familiar with the matters. Bloomberg reported that the SEC has more than 50 open inquiries spanning suspected fraud, market manipulation and breaches of fiduciary duty, although an SEC spokesperson has not yet commented on the matter. Similar alleged activity led to the arrest of Ralph Cioffi and Matthew Tannin, two fund managers from the former Bear Stearns & Cos., roughly two weeks ago. The indictment against Cioffi and Tannin alleges that the managers marketed the two funds as a low risk strategy, backed by a pool of debt securities such as mortgages, according to a statement by the Department of Justice. The indictment also alleged that by March 2007, the managers believed the funds were in grave condition and at risk of collapse, but made misrepresentations to stave off investor withdrawal. The funds subsequently collapsed in the summer of 2007, resulting in approximately $1.4 billion in losses to investors. Further indictments against Cioffi and Tannin could yet be in the offing, as well, with NPR reporting late last week that the U.S. Attorney's Office for the Eastern District of New York is pursuing additional indictments against both men.