Bank of America’s surging claims for refunds on faulty mortgages in the second quarter stemmed mostly from loans made by the bank and its Merrill Lynch unit, rather than the company’s Countrywide subsidiary, said two people with direct knowledge of the matter.

The backlog of new claims from private investors probably will increase in the months ahead, according to the people, who asked for anonymity because mortgage disputes are private. The firm regards grounds for the demands as weaker than those triggered by Countrywide loans, the people said.

Bank of America said last month that total demands for buybacks from mortgage-bond investors and insurers surged more than 40 percent in three months to $22.7 billion.