RAPID CITY, S.D. -

U.S. Sen. John Thune is requesting federal disaster aid for ranchers affected by a large prairie fire in western South Dakota.
    
Thune wrote to U.S. Agriculture Secretary Tom Vilsack on Tuesday, asking for immediate aid to ranchers affected by the Cottonwood Fire. Thune notes that many of the ranchers were hit by a winter storm three years ago.
    
The fire started Sunday afternoon east of Wall and has burned 48 square miles. Authorities say the blaze was human-caused.
    
Numerous rural buildings were burned, though no homes. Smoke from the fire cut visibility on Interstate 90 and contributed to at least two crashes. No one was hurt.
    
About 300 firefighters from 10 western counties fought the blaze at its peak.
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1 p.m.:

Authorities say a prairie fire that burned 48 square miles in western South Dakota was human-caused.
    
The Cottonwood Fire began Sunday afternoon east of Rapid City, in the Wall and Cottonwood areas. It scorched private land and part of the Buffalo Gap National Grassland. Firefighters were mopping up Monday and investigating the damage.
    
The fire burned numerous rural buildings, though no homes. It produced smoke that cut visibility on Interstate 90 and contributed to at least two crashes. It also destroyed power poles, cutting electricity to some rural areas, and killed dozens of livestock. There were no reports of any people injured.
    
About 300 firefighters from 10 western counties fought the blaze at its peak.