Merrill Lynch is expected to report today that it will add about $2.5 billion more to the $5 billion worth of write-downs it has already announced, according to a person briefed on the situation.

Merrill reports its third-quarter earnings this morning. The bank announced earlier this month that it expected to write down $5 billion because of losses in its fixed-income unit. Most of the losses, the bank said, were tied to the decline in value of complex debt instruments called collateralized debt obligations, whose value has diminished in recent months as credit markets have been hit by a collapse in the subprime mortgage market.

A Merrill spokesman declined to comment.

The additional write-down, coming so soon after the company’s $5 billion charge, may raise more questions about the leadership of E. Stanley O’Neal, Merrill’s chief executive, and the ability of his top executives to assess the firm’s risk exposure.

Since he took over in December 2002, Mr. O’Neal has pushed Merrill into riskier businesses — which, if managed well, tend to produce higher returns. That strategy has taken Merrill Lynch deeper into fixed-income markets like commodities and mortgages, areas outside of its traditional strengths of wealth management and equities.