The U.S. power regulator outlined its case of market manipulation against JPMorgan Chase & Co on Monday as industry sources said a final settlement on the issue should come on Tuesday.
Traders used improper bidding tactics in California and the Midwest to boost profits, officials said in a statement that brought to light some details of an extensive investigation.
Reports of that probe have circulated for months and a deal with the regulator could put an end to a distraction for JPMorgan Chief Executive Jamie Dimon.
The U.S. Federal Energy Regulatory Commission (FERC) staff has found "eight manipulative bidding strategies" used by a JPM affiliate in 2010 and 2011, the regulator said.
JPMorgan declined to comment.
Two industry sources said a settlement over the trades could come as early as mid-morning on Tuesday. The bank is expected to pay around $400 million to end the investigation and the settlement could include other payments, according to reports and an industry source.
Monday's regulatory move did not contain any mention of specific traders or commodities chief Blythe Masters, who had been mentioned in media reports as having been singled out by investigators.
The FERC action is a reminder of the tougher regulatory environment commodity traders are facing, particularly banks, which have been under intensifying public and political pressure over their ownership of things such as metals warehouses and power plants.
JPMorgan announced abruptly on Friday that it was quitting the physical commodity markets, seeking a buyer or partner to take over an operation that includes ownership of three power plants, as well as a handful of large tolling agreements.
The alleged violations in Monday's letter offered little new insight into the bank's trading, as most of the details had already been laid out in previous FERC filings.
If there is a settlement, JPMorgan would close the book on a probe that dates back more than two years when California's power grid operator noticed the bank was using an "abusive" trading strategy that effectively forced the grid to pay for plants to sit idle, ultimately adding to costs.
The FERC has been particularly active this month. The regulator approved a $470 million penalty against British bank Barclays Plc and four of its traders for manipulating California power markets. Barclays said it would fight the fine in court.
For JPMorgan, a deal would also allow CEO Jamie Dimon to make good on his promise to resolve multiple government investigations and regulatory run-ins over the past year. The bank, which is the biggest in the United States by assets, is under pressure in Washington for its size and for its $6.2 billion "London Whale" loss on derivatives trades last year.