California fire officials are investigating downed power lines and other utility equipment failures as possible causes of massive wildfires sweeping through wine country.
California Department of Forestry and Fire Protection spokeswoman Janet Upton says it's unclear if downed power lines and live wires resulted from fires or started them.
She said Thursday that investigators are looking into that and other possible causes.
Jennifer Robison of Pacific Gas and Electric Co. says the utility is focused on restoring power and maintaining safety. She says they will not speculate about the causes of the fires. She says PG&E will support reviews by any regulator or agency.
The California wildfires have also caused flight delays and even in some instances, cancellations. Smoke from wildfires is causing airline flights to be delayed or canceled in Northern California.
More than 80 flights were canceled by late Thursday morning at San Francisco International Airport, said airport spokesman Doug Yakel.
He says delays on other flights average 30 to 45 minutes. The Federal Aviation Administration says some arriving flights are delayed more than three hours.
Several flights are canceled at Charles M. Shulz Sonoma County Airport in Santa Rosa, near the epicenter of fires in the wine country. Airport director Jon Stout says United and Alaska each plan a flight later, and a Sun Country flight is expected if smoke is not too bad.
Wildfires have killed at least 26 people and destroyed more than 3,500 homes and businesses north of San Francisco.