Unrelenting winds sweeping California have fuelled wildfires into a fourth day - with up to a million people forced to flee their homes.It is the largest mass exodus in the United States since Hurricane Katrina, and biggest ever evacuation in the state's history, from north of Los Angeles, through San Diego to the Mexican border.One-thousand houses have been destroyed and some 470 square miles (1,220 sq km) scorched across the southern half of the state.A San Diego County official estimates losses have reached at least $1 billion (£488m).Most of the destroyed homes were in the San Diego area, where one person was killed on Sunday. Four other deaths were reported among the evacuees and more than three dozen people have been injured, including 18 firefighters.President George W Bush is due to visit California on Thursday and is expected to expand the state of emergency - which is currently in place in seven counties - to cover the whole region, clearing the way for money from Washington."If the weather co-operates maybe we can turn the tide," US Homeland Security Secretary Michael Chertoff said as he toured San Diego's Qualcomm Stadium, where 10,000 people have taken refuge. "We're still facing some very serious fires."Weather forecasters predicted fierce Santa Ana winds blowing in from the desert should begin to subside by Wednesday afternoon.A drop in the winds, which can howl at gale forces through Southern California's mountain passes and canyons, would also allow for lower temperatures and higher humidity, which could prove crucial in fighting more than a dozen wildfires still burning out of control.Governor Arnold Schwarzenegger said 68,000 homes, from cabins to luxury villas, were threatened across the state and that 10,000 men and women were working the fire lines against flames shooting as high as 100 feet (30m).© Independent Television News Limited 2007. All rights reserved.