Around half a million people in Oregon were under evacuation alerts on Friday, with residents of its largest city told to be ready to leave, as wildfires that have taken 24 lives since erupting in August tore through three US West Coast states.

About 100 wildfires in the US, West have engulfed an area nearly as large as New Jersey, belching out smoke that has given California, Oregon and Washington some of the worst air quality levels anywhere around the globe.

In hard-hit Oregon, search teams on Friday entered areas where fires burned through...