The sprawling blaze was part of a cluster of fires that burned out of control and threatened rural towns, where local officials spent the night shutting down roads and urging residents to leave their homes. The largest of the fires — which grew to nearly 800 square miles — jumped into parts of neighboring Oklahoma and remained completely uncontained as dawn broke, according to the Texas A&M Forest Service.

Authorities have not said what ignited the fires, but strong winds, dry grass and unseasonably warm temperatures have fed the blazes. Near Borger, a community of about 13,000 people, emergency officials at one point late Tuesday answered questions from panicked residents during a Facebook livestream and told them to get ready to leave if they had not already.

“It was like a ring of fire around Borger. There was no way out … all four main roads were closed,” said Adrianna Hill, 28, whose home was within about a mile of the fire. She said a northern wind that blew the fire in the opposite direction “saved our butts.”

Republican Gov. Greg Abbott issued a disaster declaration for 60 counties. The main facility that disassembles America’s nuclear arsenal paused operations Tuesday night because of the encroaching flames but said it was open for normal work on Wednesday.

The blazes tore through sparsely populated counties on the vast, high plains that are punctuated by cattle ranches and oil rigs. The main fire, known as the Smoke House Creek Fire, had grown to more than half the size of the state of Rhode Island. It is five times the size it was on Monday, when it began.

The weather forecast provided some hope for firefighters — cooler temperatures, less wind and possibly rain on Thursday. But for now, the situation was dire in some areas.

As the evacuation orders mounted Tuesday, county and city officials implored residents to turn on emergency alert services on their cellphones and be ready to evacuate immediately.

An unknown number of homes and other structures in the county were damaged or destroyed, local emergency officials said.

The Pantex plant, northeast of Amarillo, evacuated nonessential staff Tuesday night out of an “abundance of caution,” said Laef Pendergraft, a spokesperson for National Nuclear Security Administration’s Production Office at Pantex. Firefighters remained in case of an emergency.

The plant, long the main U.S. site for both assembling and disassembling atomic bombs, completed its last new bomb in 1991 and has dismantled thousands since.

Pantex tweeted early Wednesday that the facility “is open for normal day shift operations” and that all personnel were to report for duty according to their assigned schedule.

As the fires raged Tuesday, evacuations were ordered in several towns in a swath northeast of Amarillo, and officials across the border in the area of Durham, Oklahoma, also encouraged people to flee.

Texas state Sen. Kevin Sparks said an evacuation order was issued for Canadian, a town of about 2,000 about 100 miles (160 kilometers) from Amarillo. Later Tuesday, the Hemphill County Sheriff’s Office urged anyone who remained in Canadian to shelter in place or at the high school gym because roads were closed.

At least some residents in the small city of Fritch in Hutchinson County were also told to leave their homes Tuesday afternoon because another fire had jumped a highway.

“Everything south of Highway 146 in Fritch evacuate now!” city officials said on Facebook.

On Tuesday evening, the fires were 20 to 25 miles (32 to 40 kilometers) from Amarillo, and wind was blowing smoke into the city, which could affect people with respiratory issues, National Weather Service officials said.

The weather service issued red-flag warnings and fire-danger alerts for several other states through the midsection of the country, as winds of over 40 mph (64 kph) combined with warm temperatures, low humidity and dry winter vegetation to make conditions ripe for wildfires.

In central Nebraska, a mower sparked a prairie fire that burned a huge swath of grassland roughly the size of the state’s largest city of Omaha, state officials said Tuesday.

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Associated Press reporters Ken Miller in Oklahoma City, Lisa Baumann in Bellingham, Washington, and Stefanie Dazio from Los Angeles contributed.