Dozens of other wildfires are burning in Texas, which has had its worst drought in half a century
Firefighters in drought-stricken Texas are struggling to contain a 16-mile-wide (26-km) wildfire that has destroyed almost 500 homes, reports the BBC.
Officials said the fire had "grown considerably" on Monday and was now burning on 25,000 acres (10,000 ha).
Texas Governor Rick Perry cut short presidential campaigning, and said the next 48 to 72 hours would be "crucial".
Scores of fires are burning across Texas, which has been hit by high winds generated by Tropical Storm Lee.
Recent fires across Texas have burned 3.5 million acres, Perry said, adding: "That's roughly the size of Connecticut."
He urged people to heed evacuation orders and not to stay in their homes if they had lost power.
"I understand that losing your home or lifetime possessions is incredibly difficult, but do not put your life in jeopardy," Perry said.
A blaze in east Texas killed a 20-year-old woman and her baby daughter on Sunday before it was extinguished.
An estimated 5,000 people have been forced to leave their homes because of the Bastrop fire, which is about 30 miles (50km) south-east of Austin and moving away from the state capital.
Earlier, Jan Amen of the Texas Forest Service described the central Texas blaze as "a monster" that had been "zero percent contained".
The fire is the largest of dozens of wildfires burning throughout the state, including more than 60 that started on Sunday.
Powerful winds from Tropical Storm Lee, hundreds of miles to the east, have fanned the flames.
"We have about 16 miles long at this time and about six miles wide," Bastrop County Fire Chief Ronnie McDonald said, referring to the size of the biggest blaze.
It has devoured almost half of the Bastrop State Park.
Gov Perry said in a statement: "I urge Texans to take extreme caution as we continue to see the devastating effects of sweeping wildfires impacting both rural and urban areas of the state."
He has cancelled an appearance at the presidential forum in South Carolina and a trip to California.
Texas has been suffering its worst drought since the 1950s.