The program ran out of money on Thursday, leaving many small-business owners wondering how they would survive. Lawmakers are working on a deal to add $300 billion to the program.

Longstanding rules that require banks to know their customers’ backgrounds and sources of funds made it easier to take applications from existing customers rather than allow new customers access to the program. Some lenders, like Bank of America, turned away applications they received from borrowers who had gotten a loan or a credit card from another bank — a decision that a federal judge said this month was consistent with the stimulus program’s design.

However, for applications they planned to consider, the banks were supposed to handle each one as soon as it came in, not set any aside until later. The business owners who are suing say the banks did just that. Each of the lawsuits, which are seeking class-action status, claims the banks put a priority on larger loans because the banks could collect higher fees on them.

“We deny the allegations,” said Bill Halldin, a Bank of America spokesman.

The lawsuits rely heavily on two reports that the S.B.A. issued describing the types of loans it had been processing. The most recent, on Thursday, showed far more loans of $150,000 or less going through the system than a report three days earlier. This suggests, the lawsuits claim, that the banks held off on considering many smaller loan requests until they had completed the larger ones.

The S.B.A. reports do not identify banks by name. But the report on Thursday shows the largest lender, “Lender 1,” as having distributed more than $14 billion in the program. Chase released a statement a day later saying it had distributed that amount of money, more than any other lender.