The death toll in wildfires sweeping California has risen to 31, with more than 200 people still unaccounted, officials have said.

Firefighters battled on Wednesday to gain control of two wildfires burning across drought-parched foothills northeast of Los Angeles, though authorities lifted some evacuation orders as crews created a buffer around previously threatened homes. 

Fire warnings were in place across three western U.S. states on Sunday as record-breaking heat threatened to feed wildfires that have blackened thousands of acres (hectares), especially in California and New Mexico.

 Hundreds of people have evacuated to escape a wildfire in coastal Southern California and a larger blaze in rural New Mexico as hot weather feeds the flames, raising health concerns in other regions,

 Europe's forests have experienced increased disturbances throughout the 20th Century from wind, bark beetles and wildfires, a study has shown.