The Minnesota Pollution Control Agency (MPCA) has extended an air quality alert for northeast Minnesota until 4 p.m. on Thursday, May 15. The Camp House and Jenkins Creek fires in the Superior National Forest remain active and will continue to produce heavy ground-level smoke through Thursday.

Ozone is the main concern that is causing an air quality alert Monday, the Minnesota Pollution Control Agency says — but what exactly is ozone?

The Minnesota Pollution Control Agency (MPCA) has issued an air quality alert for west central, east central, central, south central, southwest, north central, and northwest Minnesota.