Fierce winds and arid conditions are threatening to feed a massive wildfire in central Oregon, a day after it killed a tractor operator who was trying to clear brush.
More than 900 households were told on Thursday to evacuate immediately or to be ready to leave as the so-called Substation Fire grew 40 per cent to 20,200 hectares on Wednesday, fire officials said on Facebook.
A Red Flag warning from the National Weather Service was in effect for the area on Thursday because of forecast winds of up to 48km/h.
On Wednesday, crews found a charred tractor and the remains nearby of its driver who was trying to clear brush in Wasco County, sheriff's officials said.
The blaze prompted Oregon Governor Kate Brown to declare an emergency in the area.
Complicating firefighting efforts was an inversion layer of thick black smoke, visible for kilometres, that has prevented water-dropping aircraft from flying into narrow canyons.
"While the smoke lifted early, it re-settled in the late afternoon, again hampering visibility and grounding aircraft," fire officials said in an alert on Wednesday.
A firefighter was killed on Saturday fighting the blaze, according to the California Department of Forestry and Fire Protection.
California has had its worst start to the fire season in a decade, with more than 89,200 hectares blackened and six major wildfires burning statewide as of Wednesday.
Australian Associated Press