Forty people have died and hundreds are still missing in California after six days of wildfires that have devastated swathes of countryside and destroyed thousands of homes.

California's governor said it was "one of the greatest tragedies" the state had ever faced.

More than 10,000 firefighters are battling 16 remaining blazes.

Winds of up to 70 km/h (45mph) brought them to new towns, forcing many more people to evacuate.