Five human feet that washed ashore on Canada's south-west coast have become an international science puzzle, and have sparked intense speculation about whether murder or a tragedy is the cause.
The fifth foot to wash up in less than 10 months was found by a passer-by on the Fraser River in a suburb of Vancouver, local police officer Sharlene Brooks said.
"[The passer-by] saw a shoe floating in the water, pulled it to the shore and called police," Ms Brooks said.
The feet are all in the care of the British Columbia Coroner's Service, which is being deluged with media calls from around the world, according to Chief Coroner Terry Smith.
"This one stretches everyone's imagination," Coroner Smith said.
"But we really need to remember that these remains are someone's loved one."
"I'm reluctant to treat this as some sort of crime thriller."
Police were tight-lipped about the type of shoe found on the fifth foot, the size of the foot, and the gender of its owner.
However, they did reveal that it is the first left foot to be found.
Annie Linteau of the Royal Canadian Mounted Police said the other four were all right feet encased in running shoes, which washed up on islands beginning last August.
Ms Linteau said the force's major crime unit was coordinating the investigation with local police.
"We're looking at all possibilities ... and that includes that they could have been connected," she said.
But Ms Linteau said it was not yet clear if a crime had been committed.
"Our examination has found no evidence that the feet were severed, meaning there were tool markings, etc."
Several experts said the feet could have been carried to western Canada on ocean currents from almost anywhere in the world.
It is also possible they originated inland in the province of British Columbia and washed down the Fraser River, said retired American oceanography Professor Curtis Ebbesmeyer of Seattle.
But finding five feet in a row, with no other body parts, suggests that "something is going on that is not natural," said Professor Ebbesmeyer, who researches how ocean currents carry floating objects around the globe.
That body parts can remain intact in water indefinitely expands the possible cause and location of origin, Professor Ebbesmeyer said.
"In a survival suit they can go for years," he said.
Criminologist Gail Anderson of Simon Fraser University, an international specialist in forensic decomposition from microbes and scavengers, said the appearance of five feet is not necessarily sinister.
"I'm beginning to think it might be a boat or plane that went down, and then something shifted, through seismic activity or a boat, that is making it release all these body parts now," she said.
"The reason only feet have been found is because they are in running shoes and protected," Ms Anderson said.
A shoe might also make a foot more likely to float, which means it could have come from "miles and miles away," she said.
Feet normally come apart from legs in water, said Ms Anderson, adding that flesh immersed in water turns into adipocere tissue, a soap-like substance, that no microbes or scavengers like crabs will eat.
Coroner Smith said the coroner's service was testing the feet for DNA while a forensic anthropologist would draw up "a broader profile of the individuals... for height, age, sex, those kinds of things".
He said the first three feet belonged to males, but tests of their DNA have not yet been matched to anyone.