Fog associated with fires in California is sending smoky plumes over the Pacific Ocean – including, potentially, north of San Diego, near the border with Mexico.
A fire has reportedly been deliberately started near the US-Mexico border.
US authorities say at least one person has died in the blaze, the so-called Cocos Fire.
The US fire command centre says the blaze has burnt more than 16,000 acres (6,650 hectares) near the San Ysidro border crossing.
San Diego County emergency officials said in a tweet that they were “actively evacuating residents” as of early on Thursday.
It said two voluntary evacuations were being carried out in a golf course near the border but had since been lifted.
“There’s no word yet if those voluntary evacuations are lifted,” it said.
A spokesman for the Federal Bureau of Investigation told reporters the fires started because one person had tried to start “something”, according to the Los Angeles Times.
Los Angeles County firefighters also reported they had a falling tree on their hands at the border.
The County said it and other local authorities were forming a task force.
The fires have been burning away from border cities such as San Diego, in the western part of the state, rather than towards Mexico.
Satellite images taken as of 1100 BST show smoke billowing from the areas north and east of the border, towards San Diego.
Earlier in the week, local media said much of the burn had been on dry chaparral underneath the earth.