The Maine Department of Environmental Protection says smoke from Canadian wildfires is again impacting air quality in Maine.

Ground-level pollution concentrations in southwest coastal Maine were in the “unhealthy for sensitive groups” level Sunday and have continued in that range into Monday. The elevated level is most likely to impact children, older adults, and people with respiratory or heart disease.

While the pollution concentration level may drop during the day Monday, another plume of wildfire smoke is expected to move in from the east and reach the Maine and New Hampshire coast by afternoon, according to the DEP. That plume from the western Canadian wildfires broke off over Newfoundland and Labrador and has now moved south into Nova Scotia.

The smoke is expected to move move out Tuesday, but it could return in the coming days as wildfires continue to burn across Canada, the DEP said.

The air quality could cause people with asthma, bronchitis, chronic obstructive pulmonary disease or other conditions to experience reduced lung function and irritation, according to the DEP.

Officials say it is possible that even healthy adults who exert themselves outside could notice side effects, such as coughing, shortness of breath, throat irritation and mild chest pain. People can protect themselves by avoiding strenuous outdoor activity, closing windows, and circulating indoor air with a fan or air conditioner.

Last week, smoke from the Canadian wildfires led the DEP to issue a similar air quality alert for much of Maine’s coastline Wednesday and Thursday.

Dozens of wildfires burning in the western provinces of Manitoba and Saskatchewan, including one more than twice the size of Los Angeles, have forced thousands of Canadians to evacuate their homes in recent weeks.