Hundreds of wildfires in Canada send hazardous smoke across the northern US

A majority of the more than 850 fires are not under control, writes the authority that monitors forest fires in the country.

Fires in northwestern Ontario have brought smoke and unhealthy air quality to the cities of Thunder Bay and Toronto.

Northwesterly winds have also carried the smoke south into the United States. Hazardous air warnings have been issued for the Great Lakes region on the border between the countries, as well as in the two northeastern US states of Michigan and Minnesota, writes the BBC.

The grey-yellow smoke from the fire has spread as far south as New York, writes the AP news agency.

Large forest fires occur annually in Canada but are becoming more frequent in the eastern parts of the country as a result of climate change, according to the BBC.