A fast-spreading wildfire in California’s wine country prompted mandatory evacuation orders as firefighters continued to battle the blaze from the ground and air into Monday.

The Pickett Fire in Northern California’s Napa County has burned some 6,803 acres since it broke out Thursday, according to the latest update from the California Department of Forestry and Fire Protection.

As of midnight Sunday local time, the fire was 11% contained with some 615 structures at threat, CalFire said.

The fire broke out around 3 p.m. local time on Thursday near the town of Calistoga, officials said. The cause of the blaze remains under investigation.

In an update Saturday on its website, CalFire said crews have been aided during the nighttime fighting of the fire by night-flying helicopters and drones.

The fire is in the same region as the massive Glass Fire that scorched more than 11,000 acres in 2020.

“Leadership with prior experience in this rugged terrain, specifically from the 2020 Glass Fire, has been instrumental in guiding effective suppression efforts,” CalFire said in its update.

The fire comes as parts of the West Coast swelter under a heat wave.

In Southern California, the extreme heat also led to elevated fire concerns, with red flag warnings in place for the mountains north of Los Angeles and Santa Barbara.

ABC News’ Tristan Maglunog contributed to this report.