Beachgoers on the West Coasts of America and Canada have stumbled upon 16 running shoes or hiking boots with rotting human feet inside since 2007.
The feet have been found on beaches in British Columbia, Canada, and Washington state.
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Last week, a hiker found a running shoe containing human flesh in a sock in British Columbia.
Speaking to CBC, his wife Charlotte Stephens, said: "He picked it up and brought it out on to the beach, and we had a look at it for about five minutes and we thought, it almost looks like there is an actual foot bone in it."
The BC Coroners Service confirmed the remains are human.
Seattle Pi reports that the series of gruesome discoveries has been dubbed the 'Nike phenomenon' as the body parts started to appear at the same time Nike started pumping air into its soles.
Two other feet discovered in British Columbia were identified as having belonged to people with mental illnesses and another three were linked to those who likely died of natural causes, the New Zealand Herald reports.
Coroner Matt Brown said most of the BC cases were determined to be suicides.
It appears that the foot disarticulated naturally from the rest of the body after prolonged immersion in water.