Firefighters have now mostly contained the blaze
Power tools used to clear brush may have sparked a fire in California that burnt 77 homes and forced 30,000 people to flee the town of Santa Barbara.
California fire officials say someone was clearing vegetation near a trail when the fire erupted on Tuesday.
State fire officials have asked the public for information about anyone who may been engaged in such activity.
Santa Barbara County residents were recently advised they had until 1 June to clear potentially hazardous brush.
It was not immediately clear whether the blaze started in an area where residents had received such a notice.
Officials have declined giving further details about the type of power tools that may have been used or if anyone could face charges.
Firefighters have contained two-thirds of the fire, aided by cooler weather and fog blowing in from the ocean. But officials remain on the alert.
"The weather tends to be a little fickle around here" said deputy fire chief Chris Hahn. "So our guard is up".
No civilian casualties have been reported since the blaze began on Tuesday but 18 firefighters have been hurt. Three suffered severe burns and smoke inhalation while attempting to put out the fire on Wednesday, fire officials said.
By late Sunday, most of the remaining 15,000 evacuees were permitted to return to their homes but were advised to remain ready to evacuate again at short notice.
Sundowners, fierce local winds that sweep down the mountains and out to sea, have been whipping up the flames in recent days as temperatures remained high.
The area's last major brush fire destroyed more than 200 homes in November. It was blamed on a bonfire started by local students.
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