An autopsy on Thursday concluded that the foot likely separated naturally from a decomposing body in the water, either by the force of waves or because of a large fish shaking the body, Martin County Sheriff William Snyder told Reuters.
"There is no evidence of man-made trauma. No cutting or sawing on it," Snyder said. "It was a clean dislocation. It just came apart."
The autopsy indicated the body part had been in the water for a period of a few days to 10 days, but could not determine the sex, race or cause of death, Snyder said.
The foot was discovered shortly after noon on Wednesday under sea grass at Peck Lake Beach at the north end of Jupiter Island, north of Palm Beach. After a ground and helicopter search over several miles, investigators found a matching shoe but no other human remains.
The shoes were all white except for the New Balance logo, estimated to be size 7-9 and described by Snyder as a running or cross-trainer style. Snyder said his gut reaction is that the victim was male.
"It's a kind of shoe I would buy and I wouldn't buy anything that looked like a woman's shoe," said Snyder, acknowledging that it is "not a scientific answer."
DNA analysis is under way, he said, and it could help identify the remains. But one potential claimant was ruled out quickly: A man who reported that his own foot had been cut off several days earlier by a boat propeller in Palm Beach County. Snyder said that man's footwear and the found shoes were not a match.
Snyder said his agency is considering the possibility that the foot may have belonged to a Juno Beach boater or a woman from Sebastian who disappeared recently in separate incidents.
Investigators also raised the possibility of the victim being a refugee who failed to make it to shore, or even a homicide victim kept in a freezer for any length of time.
Snyder said he couldn't recall another time when a body part washed up on Martin County beaches.
"It's pretty uncommon for us. But we're a coastal state. So I don't know that it's that uncommon from Key West up to Jacksonville," Snyder said.