The woman was found dead in her home in a rural area about 10 miles from Medellin, police said.
Investigators said her killers beat her to death, then poured gasoline on her body and set it afire, Colombia Reports said Sunday.
The mayor of a community in the area condemned the killing and spoke out against an "abhorrent intolerance that resembles the days of the inquisition."
Residents said the woman was accused of casting a spell on a local boy, but police said a search of her home Friday found no indication she practiced witchcraft, Colombia Reports said.
The mayor said another woman was killed in the village six years ago after she was accused of being a witch.