Workers excavating around the new outdoor riding arena at the Kentucky Horse Park on Tuesday uncovered bones of two people.
David Pollack, with the Kentucky Heritage Council, said the bones were from unmarked and previously unknown graves that probably date to the late 1800s.
Pollack said workers stopped digging and contacted authorities, who determined that the bones were not from a crime scene.
Archaeologists found human bones, some nails and hardware left from the wooden coffins, and one animal-bone button. They will return next week to scout the site for more graves and all remains will be taken to the University of Kentucky's archaeology lab for examination, Pollack said.