The fire was reported around 8:30 p.m. Thursday at Happy Valley Farms in Rossville, just south of the Georgia-Tennessee line, said Glenn Allen, a spokesman for Georgia's fire marshal.
No people were hurt in the blaze, but the damage was estimated at up to $6 million because of the value of the horses that perished. Allen described them as show horses, and said that some were valued as high as $250,000.
Allen said three buildings -- two stables and a storage facility -- were destroyed in the blaze.
The cause was still under investigation Friday afternoon.
The structure was completely engulfed within 20 minutes, Daniel Jenner, one of the farm's trainers, said in a statement.
"We were able to get one horse out of an end stall on the back side of the barn adjacent to the indoor arena," he said. "It was too hot and smoky to get anywhere near the main barn aisle."
The business is home to an expansive American Saddlebred show horse breeding and training operation, The Chattanooga Times Free Press reported. It "is one of the most widely regarded in the country," Bob Funkhouser, editor of a trade industry publication, told the newspaper.
Owner Marion "Bit" Hutcheson is widely known and respected in the industry, he said.
"Bit dedicated her life to breeding and raising world-class Saddlebreds," Funkhouser said. "The industry has benefited from her passion and commitment, and we all share in her loss."
Rossville is in Walker County, just south of Chattanooga, Tenn.
Copyright 2013 The Associated Press.