Bernard Madoff's wife withdrew $15.5 million from a Madoff-related brokerage firm in the weeks before Mr. Madoff was arrested, according to documents that raise questions about how much Mrs. Madoff knew about her husband's business, now alleged to be a Ponzi scheme that he has told authorities he perpetrated alone.

The disclosure, from the securities division of the Massachusetts Secretary of the Commonwealth, came as part of its complaint Wednesday that also offers new evidence of the close relationship between Bernard L. Madoff Investment Securities LLC and the brokerage firm, called Cohmad Securities.

Cohmad's New York operations were ensconced within the Madoff firm, some of its employees solicited investment clients for the Madoff firm and, the complaint says, the Madoff firm was Cohmad's main source of income. There is no evidence in the complaint that anyone at Cohmad knew of the alleged fraud.

The documents show Mrs. Madoff withdrew $5.5 million on Nov. 25 and $10 million on Dec. 10, the day authorities say Mr. Madoff confessed the alleged scheme to his sons and the day before his arrest.

Ira Sorkin, an attorney for both Bernard and Ruth Madoff, declined to comment, as did Irving Picard, the court-appointed trustee overseeing the Madoff firm's liquidation.