Exxon Mobil’s 251,800-barrel-per-day refinery in Joliet, Illinois, started heating its units this week, according to industry monitor IIR.
The facility lost power and took most of its units offline after a tornado passed through Joliet in July.
Earlier this week, the facility started heating the units, a crucial part of the restart process, IIR said.
The refinery may be able to restart its operations sometime in mid-August, IIR said.
“With power restored, we’re continuing to assess the status of our equipment and working hard to resume operations as quickly and safely as possible,” an Exxon spokesperson said.
Exxon did not say how long it would take to restart the refinery.
On Thursday, the U.S. Environmental Protection Agency issued an emergency waiver to help alleviate fuel shortages in states where the supply of gasoline has been impacted by the shutdown of the Joliet refinery.
The refinery mainly processes Canadian crude oil and produces around 9 million gallons a day of gasoline and diesel, according to the company website.
(Reporting by Nicole Jao; Editing by Daniel Wallis)