U.S. property and casualty insurance stocks fell in premarket trading on Friday after wildfires menacing Los Angeles killed at least 10 people and devoured nearly 10,000 structures, with five fires burning into a third night.

U.S. insurance stocks slid on Friday as analysts estimated insured losses from the wildfires menacing Los Angeles could reach as high as $20 billion, potentially making it the costliest disaster in California's history.

The massive fires that have destroyed much of Pacific Palisades and demolished more than 2,000 homes in Los Angeles County threaten an effort to fix California's troubled home insurance market.