The U.S. Department of Transportation has declared a regional emergency for Illinois, Indiana, Michigan and Wisconsin after a fire shut down the BP oil refinery in Whiting, Ind., the largest in the Midwest, though there hasn't been an impact on gas prices so far.

The federal order temporarily lifts restrictions on the maximum working hours for truck drivers in the four states.

Gov. Gretchen Whitmer (D) also signed a similar statewide energy emergency order Saturday, saying regulations "will not hinder the delivery of gas and diesel to stations in Michigan."

It's not clear when the Whiting refinery, which is the sixth largest in the U.S., will get back online....