The blaze began about 8 a.m. at a home near Cornersville, about 55 miles south of Nashville, authorities said.
Sharon Edlin stood in front of the burned-out ruins of her daughter's house and told WSMV-TV that the victims were Teresa Adams and two of her children.
Edlin said another of Adams' children, a son, was at school when the house caught fire.
Officials were still investigating the cause of the fire.
The fire was at least the fourth this week in Tennessee to result in fatalities. A brother and sister died Monday in a Chattanooga apartment fire, a Memphis woman was killed Tuesday in a fire at her home, and a Cross Plains man died Tuesday in a mobile home blaze blamed on space heaters.
For its population, Tennessee's fire death rate is twice the national average and second only to Mississippi as the worst in the country. The state reported 143 fire fatalities in 2003 and is still compiling the figures for 2004.
