The haze in the air across Austin and most of Minnesota Monday was caused by lingering smoke from wildfires in Canada and a cold front pushing through the region.

For most of Monday, the Minnesota Pollution Control Agency expanded an air pollution warning to the entire state due to smoke from the wildfires in Canada, stating the air across much of the state reached “unhealthy levels.”

Heavy smoke from Canadian wildfires slowly moved across Minnesota. As of 3 p.m. Monday, fine particle levels had reached unhealthy levels in a band across the state that included Marshall, St. Cloud, Brainerd, Duluth and Grand Portage.

All areas of Minnesota were expected to see improved air quality by Tuesday morning, but smoke could return to the state in the afternoon.

According to the National Weather Service, a cold front passed through Minnesota and parts of Wisconsin. Typically, the air behind a cold front descends through the atmosphere.

The Austin Daily Herald contributed to this report.