The Securities and Exchange Commission is investigating whether Merrill Lynch short-changed investors and gave undue influence to the hedge fund Magnetar in the creation of a $1.5-billion mortgage-backed security deal.

The investigation, which was first reported by the Financial Times ($), appears to be the agency’s first probe of Merrill Lynch’s CDO business since the financial crisis. (Check our bank investigations cheat sheet for which other firms are being probed.) Here’s the FT:

The investigation is one of several SEC probes into banks that helped underwrite billions of dollars of collateralised debt obligations, securities comprised of mortgages or derivatives linked to them.

It also marks a broadening of the SEC’s investigation into the role of collateral managers, institutions that help select the assets included in CDOs.

The deal that the SEC is investigating—a collateralized debt obligation, or CDO, called Norma—was detailed both in our reporting last year and in a report by the Financial Crisis Inquiry Commission released in January. Norma was one of more than two dozen CDO deals done by Magnetar, whose bets against a number of CDOs earned it billions in the waning days of the housing boom. 

As the FCIC detailed, Magnetar helped select the assets that went into Norma even though it had a $600 million bet that would pay off substantially if the CDO failed. As we reported, Magnetar often invested in the portion of the CDO that was riskiest and hardest for the banks to sell. Banks typically gave such investors—equity investors—more say in how the deal was structured. (Magnetar isn’t named as a target of the investigation and had no responsibility to investors. It has also maintained that it did not have a strategy to bet against the housing market.)

In the offering documents for Norma, there’s no mention of Magnetar’s role in asset selection, according to the FCIC. Investors were told that an independent collateral manager, NIR Capital Management, would be selecting the assets with their best interest in mind. The report concluded: "NIR abdicated its asset selection duties … with Merrill's knowledge." 

Bank of America, which took over Merrill Lynch in 2008, declined our request for comment. The firm’s general counsel told the Financial Crisis Inquiry Commission that it was “common industry practice” for equity investors to have input during the asset selection process, though the collateral manager had final say.

NIR Capital Management is also being investigated by the SEC, according to the FT. The firm did not immediately respond to our request for comment. (The Wall Street Journal did an impressively detailed story in 2007 on how NIR came to be manager of the Norma deal.)

Magnetar declined our earlier requests for comment on Norma, but FT reports it has denied claims that it selected the assets for Norma.

As we reported, the SEC had launched a probe of Merrill’s CDO business 2007, but that investigation petered out without any resulting charges.