More than 11 major wildfires are burning, mostly unchecked, with hundreds of thousands of residents in the San Diego and Los Angeles areas forced to evacuate as high winds fan the flames.

"Over 900 properties have been destroyed and thousands of others remain threatened," said Neena Smith, catastrophe response analyst at Risk Management Solutions.

Cholnoky said that while it was too early to assess insurer losses, it appeared that "non-traditional" companies and markets such as British-based Lloyd's might bear the brunt of the losses.

Lloyd's had no immediate comment. Neither did Nationwide. Allstate and State Farm could not be reached immediately for comment.

Eight of 10 property and casualty insurers' shares were down yesterday, and the group is underperforming a rally in the other financials. Allstate shares declined $1.16, or 2.1 percent, to $53.29 in New York Stock Exchange trading during the day.

"Most of the more traditional writers (of home insurance) have explicitly avoided writing any exposures in 'brush' defined areas," Cholnoky said in a research note.

The exception could be where winds have driven fires from these outlying areas closer to San Diego, he said.

Cholnoky said the average cost of homes in the area was about $500,000, meaning that every 100 homes lost would generate $50 million in insurance losses.

Some 250,000 people have now been ordered to evacuate ahead of the flames.

Seven of the 10 most expensive wildfires in US history, as defined by insurance losses, have occurred in California, according to the Insurance Information Institute, a group that provides industry statistics.

The largest, in Oakland and Alameda Counties in 1991, resulted in more than $2.5 billion in insured damages.