The U.S. Securities and Exchange Commission is reviewing trades in MF Global Holdings Ltd. convertible bonds to determine whether some investors sold the debt based on confidential information before the firm’s demise, according to two people with direct knowledge of the matter.

Investigators are in part focusing on trades that were made ahead of announcements that the firm’s credit rating had been downgraded, the people said, speaking on condition of anonymity because the matter isn’t public.

MF Global filed for bankruptcy Oct. 31 after concerns that it may lose money on its holdings of European sovereign debt prompted demands from regulators to boost capital, as well as credit downgrades and margin calls. Regulators are reviewing whether some investors learned in advance and traded on news that pushed the company closer to bankruptcy, the people said.

John Nester, an SEC spokesman, declined to comment. MF Global spokeswoman Diana DeSocia said it’s the company’s policy not to comment on price movements in its shares and bonds.

In one instance, MF Global’s $287.5 million of 1.875 percent convertible notes due in 2016 fell as much as 1.1 cent to 68.7 cents on the dollar on Oct. 24, one hour before Moody’s Investors Service announced that it cut the company’s credit ratings to the lowest investment-grade rating and was considering cutting it to junk, according to Trace, the bond- price reporting system of the Financial Industry Regulatory Authority.