Wildfire smoke continued to blanket northern and eastern parts of Ontario Monday, with Environment Canada issuing a warning that the very high levels of air pollution could affect vulnerable people if they don’t exercise caution.

Environment Canada has put special air quality statements in effect for the Sudbury, Elliot Lake and Prescott areas due to smoke plumes from wildfires in Ontario and Quebec, and says conditions are not likely to improve for some parts until Tuesday night or Wednesday.

Environment Canada says Quebec wildfires are also causing very high levels of air pollution in Ottawa but conditions are expected to improve Monday.

The Canadian Interagency Forest Fire Centre says there are currently 462 active fires burning across the country, with about 237 of them deemed out of control and almost one-quarter of those fires are in Quebec.

In its air quality statement Environment Canada says that people with lung disease, heart disease, older adults, children, pregnant people, and people who work outdoors are at higher risk of experiencing health effects caused by smoke.

The agency is advising locals to stay indoors with their windows closed, use an air purifier if possible and check on loved ones.