When Lehman Brothers collapsed at the height of the financial crisis, JPMorgan Chase was at the center of the storm. The bank was a major lender to the firm, which filed the biggest bankruptcy in U.S. history.

Now, more than three years later, regulators are set to penalize JPMorgan for actions tied to Lehman's demise, according to people briefed on the matter. It will be the first federal enforcement case to stem from Lehman's downfall.

The Commodity Futures Trading Commission is expected this week to file a civil case against JPMorgan. The bank is expected to settle the Lehman matter and pay a fine of approximately $20 million. While the penalty is significant for the agency, the sum is little more than a rounding error for a bank as large as JPMorgan.

The Lehman action stems from the questionable treatment of customer money -- an issue that has been at the forefront of the recent outcry over MF Global. JPMorgan was also intimately involved in the final days of that brokerage firm.

The trading commission is expected to accuse JPMorgan of overextending credit to Lehman for two years leading up to its bankruptcy in 2008, the people briefed on the matter said.

JPMorgan extended the credit using an inaccurate evaluation of Lehman's worth, improperly counting Lehman's customer money as belonging to the firm. Under federal law, firms are not allowed to use customer money to secure or extend credit.

The arrangement worked well for both parties, according to the people briefed on the matter, who spoke on the condition of anonymity because the case was not yet public. Lehman wanted a larger loan, and suggested counting money from the customer account to justify it. JPMorgan complied, counting the money as part of Lehman's coffers.

It is unclear whether JPMorgan knew the money belonged to clients. But in the view of regulators, it should have -- the customer funds were kept at a JPMorgan account.

The agency is also set to accuse JPMorgan of withholding separate Lehman customer funds for nearly two weeks, rather than turning them over to authorities, the people said. In the course of resolving that matter, regulators became aware of JPMorgan's questionable credit to Lehman, one of the people briefed on the matter said.

JPMorgan declined to comment. The bank is expected to neither admit nor deny wrongdoing in the settlement.

The trading commission's action against JPMorgan is the latest prominent action filed by the Commodity Futures Trading Commission, once thought of as a sleepy regulator. On Monday, the agency sued the Royal Bank of Canada, accusing it of operating a trading scheme that it used to reap lucrative tax benefits.