The newspaper cites "people familiar with the case" who said the Justice Department decided to look into energy practices after JPMorgan agreed in July to pay $410 million to settle claims from the Federal Energy Regulatory Commission it cheated regional markets in California and the Midwest.
FERC in July said the bank carried out "manipulative bidding strategies" from 2010 to 2012.
"The regulator said JPMorgan devised ways to turn money-losing power plants into profitable assets, focusing in part on maximizing payments designed to compensate power providers when prices fall," the Journal reported.
The newspaper reported JPMorgan announced plans in July to unload its commodities assets related in part to trading desks that buy and sell oil, natural gas, electric power and coal. Citing people familiar with the sale, the Journal reported the bank, one of the nation's largest, could sell off its holdings early next month.