OMAHA, Neb. (AP) – Wind and dry heat helped whip the flames of a Nebraska wildfire that grew by nearly 78 square miles in one day.

The fire between Chadron and Rushville in the northwest corner of the state grew by Saturday to more than 93 square miles – an area bigger than Nebraska's state capital of Lincoln. It also crossed the state line into South Dakota, forcing the evacuations of several communities there, along with residents on a rural county road on the Nebraska side, Nebraska Emergency Management Agency spokeswoman Jodie Fawl said.

In South Dakota, the fire burned more than 27,000 acres on the Pine Ridge Indian Reservation, NEMA official Roger Conrad said Saturday evening.

“High winds just blew that thing out of control, from what crews were telling us,” he said. He had no estimate of containment.

Pine Ridge Bureau of Indian Affairs agency deputy superintendent Harold Compton said earlier in the day that the fire had destroyed a home and a couple of structures. Oglala Sioux Tribe President John Yellow Bird Steele had issued an evacuation order for residents of Slim Buttes, Calico, Tobacco, Number 4 Payabaya, Lakeside and Oglala.

Triple-digit temperatures, low humidity and gusty winds didn't help Saturday's efforts to fight the flames.

“We don't consider ourselves out of the woods,” Compton said.

The National Weather Service issued a red flag warning until 11 p.m. Saturday, indicating a high wildfire risk throughout western South Dakota and the northwestern corner of Nebraska.

The blaze is one of three large wildfires sparked by lightning earlier in the week in the tinder-dry northwestern corner of Nebraska, a sparsely populated area of rolling prairie hills, badlands and stands of Ponderosa pines.

Two fires burning to the west – one south of Chadron and another between Harrison and Crawford – were being measured together on Saturday. As of Saturday night, they had burned 87,555 acres and were 47 percent contained, said Cyd Janssen, public information officer with the fire's operation center.

The expansion of the flames did force the evacuation overnight of Whitney, a Nebraska town of about 75 people, but firefighters managed to stop the flames within a mile of the small town.

Crews were beginning mop-up operations on the third fire, a collection of fires that moved through Keith, Lincoln and McPherson counties, which was 15 miles long, 2 miles wide and 90 percent contained, Conrad said Saturday night.

Gov. Dave Heineman announced Saturday that he planned to tour the scorched areas on Sunday and meet with local and state responders and firefighters in the Rushville, Crawford and Chadron areas.

Sheila French, a spokeswoman for the operations center for the two most western fires, said hundreds of firefighters poured into the area Friday night and into Saturday, taking the number of people fighting the fires from 214 on Friday to nearly 500 and counting Saturday.

“We have vehicles from Alaska, Arizona ... New York; there are people from all over the country here,” French said.

Three minor injuries have been reported from the fires. No deaths have been reported, but authorities said a 64-year-old woman died of an apparent heart attack after she was evacuated from her home Wednesday night.

At least one Nebraska home and one South Dakota home have been destroyed in the fires, officials said, and dozens of farm buildings are believed to have been destroyed.

“But we won't have any kind of numbers on that until officials can get in the area and see what we're dealing with,” Fawl said.

A cold front was expected to move through the region late Saturday night, bringing much-anticipated cooler temperatures and a favorable shift in winds, French said. But the system wasn't expected to bring much rain, and lightning could spark more fires in the drought-parched region.

The American Red Cross has disaster relief workers in the area to help provide food and shelter to those evacuated from their homes, as well as meals to those helping fight the fires. The Red Cross has set up shelters at St. Patrick's Assumption Arena in Chadron and Hope Baptist Mission in Rushville.

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Associated Press writer Dirk Lammers in Sioux Falls, S.D., contributed to this report.