State Forest Service spokesman Chris Meggs said a planned burnout operation Sunday to fight the fire by eliminating combustible materials failed to stop the blaze, known as the Simmons Road Fire.
"The fire came through our lines due to erratic winds and dry conditions," Meggs said.
Burning across the area's flammable organic soil, the blaze continued moving northward into Cumberland County, where residents in 10 homes were given mandatory evacuation orders on Monday. A shelter was opened at Cape Fear High School near Fayetteville to house the evacuees.
A cabin and two outbuildings were lost in the fire Monday, along with a four-wheeler and a specialized tractor used to fight wildfires, Meggs said.
The blaze was sparked by lightning June 20 and consumed three homes in the first 48 hours. Firefighters were able to contain the blaze to slightly more than 3,000 acres until Sunday, when it expanded by another 2,850 acres.
Meggs said Tuesday that the total size was likely to grow to an estimated 6,000 acres by the end of the day.
With 78 firefighters, eight fire engines and two helicopters assigned to the Simmons Road blaze, the cost to fight the fire already has exceeded $600,000, forestry officials said.
A 31,000-acre blaze in Pender County, known as the Juniper Road Fire, is has used $2 million in firefighting resources since it started June 19. The fire is considered percent contained.
More than 150 firefighters are still working on the Pender County blaze, which is burning primarily in the Holly Shelter Game Land.
A 45,000 acre fire in Dare County is considered 100 percent contained, but continues to burn fed by fuel in the organic soils, officials said.
The state has issued a ban on open burning in response to a spate of wildfires and continuing dry conditions,