Satellite images have revealed the scale of two wildfires spreading in southern California.
The Sandy Fire ignited on Monday morning in the city of Simi Valley, north-west of Los Angeles, according to California Governor Gavin Newsom.
Satellite images taken just after noon local time (20:00 BST) on Monday show a large plume of smoke rising into the air just south of the city.
California fire officials said on Tuesday morning that 750 firefighters were being supported by night-flying water dropping helicopters to target hotspots.
The Simi Valley Police Department said it had received a report that an individual hit a rock with a tractor, which sparked the fire, according to the BBC's US news partner CBS.
The fire had since spread across 1,364 acres (550 hectares) and no part of it has been contained, officials said.
Data from Nasa's wildfire monitoring platform shows active hotspots moving further south overnight into Tuesday.
More than 10,000 homes have been evacuated from Simi Valley and surrounding communities, Newsom said.
A further 3,500 homes are under evacuation warnings, extending into neighbouring Los Angeles county
Los Angeles mayor Karen Bass said officials don't expect the blaze to spread to the city but warnings have been issued out of an abundance of caution.
The spread of the fire was helped by high winds on Monday morning that eased later in the day, a fire department spokesperson said.
Simi Valley Unified School District officials said classes would be cancelled on all of its campuses on Tuesday.
Satellite images also show a fire on Santa Rosa Island off the coast of Los Angeles that has burned 14,600 acres (6,000 hectares) of the Channel Islands National Park, according to the US National Park Service.
