By Suzi Parker

LITTLE ROCK, Arkansas (Reuters) - Firefighters in three Nebraska counties battled expanding wildfires on Wednesday and an Arkansas town of 1,300 people was evacuated because of an approaching fire, as the central part of the United States suffered through another day of stifling heat.

Authorities evacuated the entire town of Ola, Arkansas, population 1,300 people, on Wednesday afternoon because of an encroaching wildfire. The town, 74 miles west of Little Rock, was especially vulnerable because a warehouse in which fireworks were stored is feared to be in the path of the flames.

The fire jumped a highway and also forced the evacuation of a rural area near Ola, authorities said. There have so far been no injuries or deaths from the Arkansas blaze so far.

While the Arkansas wildfire itself is small, burning only about 100 acres so far, a dispatcher for the Yell County Office of Emergency Management said only about 50 percent of the fire had been contained.

Much larger fires were raging in Nebraska, where some 72,400 acres had been consumed in the drought-stricken north central region of the state by Wednesday, authorities said.

Weeks of 100-plus Fahrenheit (38 Celsius) temperatures have destroyed many dryland crops across Nebraska, leaving areas more susceptible to wildfires and making conditions for firefighters nearly unbearable.

Crops on irrigated land in the state still show some promise, but the National Weather Service predicts little chance of significant rain in the near future.

Lightning strikes apparently sparked wildfires in the scenic Niobrara River Valley on Friday. Firefighters were just beginning to make progress on those blazes on Wednesday. They were aided by air drops from several helicopters.

A portion of the Niobrara River was declared off limits for public use and a part of Nebraska Highway 12 was closed earlier, but reopened on Wednesday afternoon.

Governor Dave Heineman met on Tuesday with federal, state and local workers responding to fires in Brown, Keya Paha and Cherry Counties. He had issued an emergency declaration statewide at the start of July for drought and fires.

Unlike the Arkansas fire and those that struck Colorado earlier in the summer, forcing an exodus from several communities including Colorado Springs, the Nebraska wildfires have so far been limited to sparsely populated areas.

The governor's office said 10 structures and some associated outbuildings had been destroyed and about 80 were threatened. Several Nebraska state agencies were responding to the blazes.

The three wildfires burning in the vicinity of the town of Ainsworth had consumed just over 72,400 acres as of Wednesday, according to the federal fire incident command center. The biggest, called the Fairfield Creek Fire, was 66,745 acres and straddles a river.

"Over the last two days, temperatures above 100 degrees and low humidity with Red Flag Warnings have created extreme fire behavior and difficult conditions for fire fighters," according to the fire incident command center.

The Ainsworth area Chamber of Commerce pleaded for help on Wednesday, citing the loss of grazing land for cattle and the loss of structures. Donations will be used to buy feed and hay for cattle, fencing supplies and other ranching needs, it said on its website.

(Additional reporting by Michael Avok; editing by David Bailey, Greg McCune and Todd Eastham)