Inside the investment houses, several traders said nerves were frazzled further by worries that banks could face much bigger mortgage related losses, not from foreclosures, but because of questions about how the money was lent in the first place. If it turns out that mortgages were bundled together and sold improperly, more holders could sue the banks and force them to buy back tens of billions in mortgage-backed securities.

An alarming report on Bank of America, compiled by Branch Hill Capital, a San Francisco hedge fund, circulated widely on Wall Street on Thursday. Branch Hill suggested that the bank, the nation’s largest, could be facing more than $70 billion in losses from mortgage securities that it may have to repurchase from Fannie Mae and Freddie Mac, as well as private investors.

“We think this is a very important issue, and the liability will be substantial,” said Manal Mehta, a partner at Branch Hill. “There has been pervasive bad behavior throughout the system.” The fund is betting that Bank of America shares could decline because of the potential liability.

Bank of America declined to comment Thursday. But the company’s chief executive, Brian T. Moynihan, said last month at an investor conference that adequate reserves had been taken to protect against any losses that could materialize if it was forced to repurchase mortgage securities. “This will be manageable over time, but it has cost us a lot of money so I’m not making light of it,” he said. “We’ll continue to manage it.”

On Wednesday, JPMorgan said it had added $1 billion to its reserves to cover faulty home loans that it was obligated to repurchase from Fannie Mae, Freddie Mac and private insurers. It has set aside a total of $3 billion for potential repurchases.

Even if the larger losses envisioned by Mr. Mehta do not materialize, the foreclosure issue remains a worry. In a report, Paul Miller, an analyst with FBR Capital Markets, forecast that the controversy would cost the banking industry $6 billion to $10 billion. He estimated that each month’s delay cost the banks $1,000 per home loan, so if there was a three-month delay on the roughly two million homes currently in foreclosure, that translated into a $6 billion hit.