A layer of haze covers the view of Pikes Peak rising over the south Denver metro area on Sunday, Nov. 4, 2018. (Jesse Paul, The Colorado Sun)

The U.S. Environmental Protection Agency says Denver and parts of northern Colorado failed to meet ozone pollution standards, and it will direct the state to come up with a new plan to clean up the air.

The EPA announced Thursday it plans to downgrade the area’s status from moderate to serious. The classifications refer to how far out of compliance the area is with agency standards.

MORE: Front Range air quality is terrible, but Colorado’s efforts are showing some improvement in ozone pollution

The move was expected after Democratic Gov. Jared Polis said in March the state wouldn’t ask for an exemption based on pollution drifting into Colorado from China and elsewhere.

Jill Hunsaker Ryan, director of the state health department, says Colorado is already working on steps to reduce pollution, including writing new rules for the oil and gas industry and encouraging more electric cars.