A wildfire driven by California's dry, seasonal Santa Ana winds rapidly expanded to more than 12,500 hectares overnight outside Los Angeles, forcing widening evacuations on Tuesday.
When he took his first leave, Zuckerberg wrote that he's "pretty sure the office will still be standing when I get back".
Hundreds of firefighters were working through the night to try to prevent the fire from reaching Santa Paula and Ventura cities.
The winter months are usually when Southern California sees Santa Ana winds, which have been responsible for some of the region's most catastrophic fires.
Los Angeles Police Department Chief Charlie Beck urged local residents to evacuate immediately if they were told to leave, noting that strong winds are expected to continue through at least Thursday.
What's it looking like for firefighters?
It was reported that one person died in a road accident whilst trying to flee his home. ABC7 has continuous coverage of fires burning in SoCalMultiple homes in the area of Scenic Way Drive in Ventura could be seen burning from the air.
Evacuation shelters are open at the Ventura County Fairgrounds at Miners Building.
Several hashtags about the fire, including #ThomasFire, #Ventura and #Santa Paula, were trending on Twitter early Tuesday morning, as people shared striking photos of the fast-moving blaze.
California wildfire forces 27000 to flee, burns 45000 acres, still no containment
More than 8,000 homes were evacuated and 20,000 people remained without power Tuesday. The east-to-west blowing winds come from the Pacific and tap into warm and dry conditions inland.
Los Angeles mayor Eric Garcetti declared a state of emergency in the city late Tuesday, advising that the fire covered some 11,000 acres. So far, 505,391 acres have burned this year, up from up from 244,297 acres at this time in 2016.
Following are scenes of the wildfire throughout the night.
Deteriorating air quality caused by a colossal fire in nearby Ventura County has also impacted students enrolled in classes of the Santa Monica-Malibu Unified School District.
Smoke billows over Ventura on December 5.
The federal government, after a nearly yearlong delay by the Trump administration, moved after the North Bay fires to require wireless carriers to upgrade the alert system to target areas more specifically.
The fire started Monday evening somewhere near California State Highway 150 and later grew toward Santa Paula in an area about 65 miles northwest of Los Angeles, the Los Angeles Times reported.
In some areas, the winds made it impossible for firefighters to use airplanes to attack the fire, officials said.