As many as 500 homes were in danger and more evacuations had been ordered near the Lower Lake area of northern California late Sunday as a fast-moving blaze continued to roar through the area.

By Sunday, fire officials reported the Clayton blaze had spread to consume more than 1,400 acres and had already totally destroyed at least four structures. The cause of the fire, about 100 miles north of San Francisco, remained a mystery.

Third Blaze in Days

The third to strike the Lake County area in a span of just 96 hours, the blaze broke out just before 5 p.m. Saturday and quickly began to char the area. By early Sunday, fire officials reported it was back down to just five percent containment.

 Meanwhile, mandatory evacuations have been ordered for the areas of Clayton Creek Road, Morgan Valley Road to Butte Rock Ranch Road (including all streets east of Highway 53), Ellen Springs Drive, Spruce Grove Road, Staele Lane, Black Bass Pass Road and Lake Bridge Road.

An emergency shelter was also set up at the Highland Senior Center near Clearlake, with about a dozen people taking refuge there Saturday night.

On Sunday, sweltering temperatures topping out in the lows 90s and winds of about 10 mph only added to the difficult task firefighters already faced.

Fire Officials Working Around the Clock 

As many as 675 fire officials have been assigned to battle the blaze, with 18 water tenders, 21 bulldozers and four helicopters being among the equipment being used. 

"We've hit the critical point where all the fuels are dry, and last night the fire remained active throughout the night, so that doesn't forecast a very good day for us," said Cal Fire spokeswoman Suzie Blankenship. "Things are very intensely burning."

The blaze is reported to be consuming an area spared by last year's Valley Rock and Jerusalem fires that charred more than 170,000 acres, destroyed 2,078 structures and killed four people.