Thousands of residents flee as the largest wildfire west of Sacramento in California almost doubled in size, spanning 54,000 acres Sunday, up from the estimated 27,000 acres reported the previous night, various media reported.

California Department of Forestry and Fire Protection or Cal Fire spokesman Daniel Berlant told NBC News that only five percent of the Rocky Fire in Lake, Colusa and Yolo counties was contained late Sunday afternoon as the dry weather condition caused by the drought is feeding the fire. More than 12,000 people have already fled the affected areas and authorities have ordered the closure of several highways.

"This has been a very fast-moving wildfire with the dry conditions and the weather not really cooperating with us over the past week," Berlant told CNN affiliate KCRA.

This "is a very dangerous fire," he added

Dozens of buildings - including two-dozen homes - had been destroyed, and 6,000 more buildings remained threatened by the fire, which was sparked in the drought-stricken state on Wednesday and exploded in size amid dry, windy conditions on Saturday, Berlant said.

Berland posted on his Twitter account, @CALFIRE_PIO, "#RockyFire has grown to 54,000 acres & 5% contained. Nearly 2,000 firefighters tirelessly working to contain the fire

9:36 AM - 3 Aug 2015."

Firefighters estimated that the wildfire, which was first reported on Wednesday, has engulfed dozens of buildings, including 24 homes. At least 6,000 more buildings are threatened by the growing fire, Berlant said.

More than 2,000 firefighters, 180 engines, four air tankers and 19 helicopters are involved in battling the Rocky Fire, and an additional 6,000 personnel are trying to control some 20 other large fires across the state, stretching from the San Diego to the south of the Oregon border.

Authorities reported that one firefighter was killed on Saturday while battling the so-called Frog Fire, some 100 miles south of Oregon.

California Gov. Jerry Brown and his wife extended their condolences to the family of U.S. Forest Service Firefighter Dave Ruhl, the lone fatality of the wildfire so far. Brown said he and wife were "saddened to learn of the tragic death of Ruhl" who left his home state to help in containing the fire in one of "California's majestic forests."

Brown has declared a state of emergency Friday to mobilize additional personnel and resources to battle the fires. "California's severe drought and extreme weather have turned much of the state into a tinderbox," he said.

Berlant added firefighters were overwhelmed at the speed which the fires spread even at a time when they were supposed to be gaining some grounds. Firefighters usually gain some headway during the night time as humidity rises and fire activity die down. However, the Rocky Fire did the opposite and spread quickly overnight.

"This fire was very active throughout the night," he told KCRA. "It was really burning very fast, all the way up into the late hours, so unfortunately we're really not getting a break."

Also, contributing to the problem are the lightning strikes which have ignited several hundred small fires in the northern part of California, Berlant added.