Canada wildfires smoke could linger over parts of US for days, officials warn

Millions of Americans remain under air pollution warnings as schools close and air travel is disrupted

Toxic smoke from Canadian wildfires could linger over vast swathes of the US for days, officials warned, as millions of Americans remained under air pollution warnings.

Across the eastern US residents were again urged to stay inside and limit or avoid outdoor activities on Thursday, as schools in some cities closed, sporting events were canceled, and air travel was disrupted.