SOUTH LAKE TAHOE, Calif. (AP) A California fire that gutted hundreds of homes advanced toward Lake Tahoe on Wednesday as thousands of firefighters tried to box in the flames and tourists who hoped to boat or swim were enveloped in a thick yellow haze of the nations worst air.

The Caldor Fire spread to within 20 miles (32 kilometers) east of the lake that straddles the California-Nevada state line, eating its way through rugged timberlands and knocking on the door of the Lake Tahoe basin, Californias state fire chief Thom Porter warned this week.

Ash rained down on Tuesday and tourists ducked into cafes, outdoor gear shops and casinos on Lake Tahoe Boulevard for a respite from the unhealthy air.