Smoke from Canadian wildfires is working its way into the northern U.S. this week, prompting warnings from health officials that air quality may become briefly unsafe.

According to the Environmental Protection Agency's AirNow air quality map, parts of North Dakota, Minnesota and Michigan registered warnings for moderate air quality on Friday. In some places within that stretch, the map showed a level of air quality considered unhealthy for sensitive groups.

Officials say the plume of wind-driven smoke is expected to make air quality worse over the coming days, possibly to a point that becomes unsafe for the general population. The North Dakota Department of Environmental Quality recommended on Friday that people limit their time outside, to reduce their exposure to the smoke.

RELATED STORY | Nearly half of Americans are breathing in unhealthy levels of polluted air, report says

The smoke comes from fires in Manitoba, Canada, which have forced evacuations of thousands of people. The fires are burning during Canada's wildfire season, which officially begins in May and will continue through September.

According to the EPA, the fine particles from wildfire smoke can cause eye, nose and throat irritation. Exposure may also aggravate pre-existing breathing and heart conditions and increase the risk of asthma, heart failure and premature death.

When wildfire smoke is present, the EPA recommends staying indoors with sealed windows, limiting time outside and wearing respirator masks.