The banking industry says it is simply serving customers who have authorized the lenders to withdraw money from their accounts. “The industry is not in a position to monitor customer accounts to see where their payments are going,” said Virginia O’Neill, senior counsel with the American Bankers Association.

But state and federal officials are taking aim at the banks’ role at a time when authorities are increasing their efforts to clamp down on payday lending and its practice of providing quick money to borrowers who need cash.

The Federal Deposit Insurance Corporation and the Consumer Financial Protection Bureau are examining banks’ roles in the online loans, according to several people with direct knowledge of the matter. Benjamin M. Lawsky, who heads New York State’s Department of Financial Services, is investigating how banks enable the online lenders to skirt New York law and make loans to residents of the state, where interest rates are capped at 25 percent.

For the banks, it can be a lucrative partnership. At first blush, processing automatic withdrawals hardly seems like a source of profit. But many customers are already on shaky financial footing. The withdrawals often set off a cascade of fees from problems like overdrafts. Roughly 27 percent of payday loan borrowers say that the loans caused them to overdraw their accounts, according to a report released this month by the Pew Charitable Trusts. That fee income is coveted, given that financial regulations limiting fees on debit and credit cards have cost banks billions of dollars.

Some state and federal authorities say the banks’ role in enabling the lenders has frustrated government efforts to shield people from predatory loans — an issue that gained urgency after reckless mortgage lending helped precipitate the 2008 financial crisis.