HARRISBURG, Pa. (AP) -- The U.S. Department of Energy has ordered another power plant, this time an oil and gas plant in Pennsylvania, to keep its turbines running through the hottest summer months as a precaution against electricity shortfalls in the 13-state mid-Atlantic grid.

The department's order to the grid operator, PJM Interconnection, regarding the Eddystone power plant just south of Philadelphia on the Delaware River, is the department's second use of federal power under President Donald Trump to require a power plant to keep operating on the mainland United States.

Constellation Energy had planned to shut down Eddystone's units 3 and 4 on Saturday, but Trump's Department of Energy ordered the company to continue operating the units until at least Aug. 28. The units can produce a combined 760 megawatts.

The department, in its order, cited PJM's growing concerns about power shortfalls amid the shutdown of aging power plants and rising electricity demand.

PJM last year approved Constellation's request to shut down the units, but it welcomed the department's order to keep them operating, saying it's a "prudent, term-limited step" that allows PJM, the department and Constellation to study the longer-term need and viability of Eddystone's units.

The department took a similar step last week, ordering Consumers Energy to keep the J.H. Campbell coal-fired power plant open in Michigan past its Saturday retirement.

The grid operator there, the Midcontinent Independent System Operator, said the order was unnecessary, that there was no energy emergency there and that there should be enough energy in the region through the summer.

An environmental advocacy group, the Delaware Riverkeeper Network, criticized the move to keep Eddystone operating as an "environmental injustice." Shutting down the units would reduce hazardous pollution and carbon emissions from the decades-old facility and help the region meet federal clean air standards for smog, it said.