Governor Greg Abbott issued a disaster declaration for 60 counties on Tuesday as the largest fire burned more than 1000 square kilometres, according to the Texas A&M Forest Service.
That is more than twice its size since the fire sparked on Monday.
Authorities have not said what might have caused the blaze, which tore through sparsely populated counties surrounded by rolling plains.
"Texans are urged to limit activities that could create sparks and take precautions to keep their loved ones safe," Abbott said.
The largest blaze, known as the Smokehouse Creek fire, closed highways and remained uncontained as of Tuesday afternoon, according to the forest service.
The main facility that assembles and disassembles America's nuclear arsenal shut down its operations on Tuesday night in Texas as fires raged out of control near its facility.
Pantex issued a statement online saying it had paused operations until further notice.
"The fire near Pantex is not contained," the company said.
"Response efforts have shifted to evacuations. There is a small number of non-essential personnel sheltered on-site."
Since 1975, Pantex has been the US's main assembly and disassembly site for its atomic bombs.Â
It assembled the last new bomb in 1991 and has dismantled thousands of weapons since then.
Multiple fires were reported across Hemphill and Hutchinson counties near the Oklahoma border, where some evacuations and school closures were also ordered.
Fire officials across the border in the area of Durham, Oklahoma, also encouraged people to evacuate because of the fire.
