Robert Rubin, a senior adviser to Citigroup Inc. at the time of its deep losses from subprime mortgages, says he learned belatedly that Citi had $43 billion in high-risk securities on its books.

Rubin says, "I do not recall knowing before September 2007" that the bank had held onto the investments composed of repackaged mortgage bonds. In November 2007, Citigroup publicly estimated it would lose $8 billion to $11 billion in the fourth quarter that year from those securities.

Rubin, a former Treasury secretary, makes the statements in testimony to a panel investigating the roots of the financial crisis. He and other former Citigroup executives have been sharply criticized for allowing heavy investments in high-risk securities. Citi was a major subprime lender.