Oct 26 (Reuters) - Cool, damp weather helped firefighters gain the upper hand on Friday in their six-day-long struggle with wildfires across Southern California.

At least one is being investigated as arson and many others are thought to have been started by power lines brought down by hot gusting Santa Ana winds onto brush parched by a record drought. High temperatures and winds whipped the fires and sent embers flying for miles, setting off new fires.

Following are some numbers:

* 16 active fires from Los Angeles County to the Mexican border.

* At least one being treated as arson.

* More than 500,000 people evacuated at height of fires, largest number in California history, most in the San Diego area. Most evacuation orders lifted by Friday.

* Some 2,000 homes and at least 180 commercial buildings destroyed or damaged.

* At least 12 people dead, more than 60 injured, most of them firefighters.

* 810 square miles (2,100 sq km) burned, an area more than twice the size of New York City.

* Seven Southern California counties declared major disaster areas.

* Overall insured losses expected to be up to $1.6 billion, including $1 billion in San Diego County.

* About 12,000 firefighters battling flames.

* Federal Emergency Management Agency has 1,000 people on the ground across Southern California.

Sources: California Office of Emergency Services; San Diego County.

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