Authorities are investigating how a U.S. farmer was eaten by his hogs.

The district attorney's office says 70-year-old Terry Vance Garner never returned after he set out to feed his animals Wednesday on his farm near the Oregon coast.

A family member later found Garner's dentures and pieces of his body in the hog enclosure, but most of his remains had been consumed.

The district attorney's office said in a statement Monday that it's possible Garner had a medical emergency, such as a heart attack, or was knocked over by the animals before he was killed. But criminal activity has not been ruled out.

Authorities estimate the hogs weigh 700 pounds (320 kilograms). The DA's office says one hog had either bitten or been aggressive with Garner previously.