NEW YORK ( TheStreet) -- Ambac Financial Group ( ABK) filed for Chapter 11 bankruptcy today, one week after announcing it would miss an interest payment on a portion of its outstanding debt. The monoline insurer filed for bankruptcy in the United States Bankruptcy Court for the Southern District of New York. As of June 30, 2010, Ambac had debt of $1,622 million, according to a company statement. Last week the company warned the board that it was declining to make an interest payment on the company's debt due November 15 . Earlier this year, TheStreet explored what form a prepackaged bankruptcy may take in case Ambac explored that option.