EDINBURGH, Scotland (AP) — Scottish scientists are investigating the mysterious deaths of seals found with horrific corkscrew injuries the length of their bodies, officials said Friday.

Over the past nine months, about 30 badly mutilated gray and common harbor seals have washed up on Britain's east coast, ranging from Scotland in the north to Norfolk in the south.

The mammals were found with a smooth-edged cut, starting from the head and spiraling around their bodies down to their abdomens in a single sweep.

Autopsies failed to reveal a cause of the injuries, and scientists from the Sea Mammal Research Unit at St. Andrews University in Scotland are now coordinating the investigation on behalf of the Scottish government, the Royal Society for the Protection of Animals and the National Trust.

"We cannot rule out that this has been caused by a predator, but given the injuries we have seen, our best guess at the moment is that it was caused by some sort of ducted propeller," said Dave Thompson, a senior research scientist at the St. Andrews unit.

"It is unlikely to be a ship's propeller, because that leaves a different and distinctive form of injury. We believe it might be happening in a confined device," he said. "What is strange is that the seals appear to be entering the device head first. We don't know why this is at the moment."

In the last two months, seven mutilated seals were found in St. Andrews Bay and the Firth of Forth estuary near Edinburgh. About 20 carcasses have washed up on the Norfolk coast, an area about 130 miles (210 kilometers) northeast of London.

The mammal research unit said the populations of common or harbor seals and gray seals in Scotland has been in decline. A 2008 Scottish government report estimated there are about 164,000 gray seals and 20,000 common seals off the shore of Scotland.

It has asked the public to report any sightings of mutilated seals washed ashore.

"It is critical that we establish the cause of these strange seal deaths and do all we can to protect our seal populations, particularly as numbers have reduced in recent years," Scotland's environment secretary Richard Lochhead said in a statement.

A number of similarly mutilated seal carcasses have been found off the Atlantic coast of Canada, but scientists there believe the injuries may have been caused by sharks.