A controlled burn in the Quantico, Virginia, area created smoky conditions in the D.C. area Sunday.
Marine Corps Base Quantico conducted the burn from 10 a.m. to 1 p.m.
The burn covered about 2,000 acres, according to Arlington County police.
Prince William County advised people with respiratory illnesses or conditions aggravated by smoke to remain indoors until the smoke clears.
The National Weather Service said the smoke appeared on its radar.