Canadian wildfires in Manitoba and Saskatchewan have prompted air quality alerts in Minnesota, Wisconsin and Michigan on Wednesday and Thursday as residents are advised to "limit prolonged or heavy exertion.

State officials from Maine to New York issued alerts for fine particulate matter, a toxic byproduct of wildfires that is small enough to be inhaled.

Officials warned young children and those with respiratory illnesses to take precautions. For weeks, smoke from Canadian wildfires has been drifting across the border.