On an ordinary day, beachcombers roaming the rocky shores of Newfoundland can hope to find treasures like mermaid’s purses, barnacle shells and a rainbow’s worth of sea-polished glass fragments. The oddest thing might be the occasional moose teeth, tools or even a doll’s head.

Weird, white mystery blobs are another matter.

“It’s the first time I’ve ever seen anything like it, and I’ve lived right here in Placentia Bay my whole life,” said David McGrath, a 67-year-old retiree who stumbled across the mysterious newcomers last month.

The Canadian Coast Guard was notified. Beaches on the southern shores of the North Atlantic isle were briefly roped off. A federal agency began investigating.

The blobs range in size from a coin to a dinner plate. They come in an almost pristine white before mixing with sand and turning darker. They are sticky. And they are — this the main thing — indisputably blobby.

After that, there is some disagreement.

Some say the blobs carry a whiff of odor not unlike paint.

But Mr. McGrath said he had not detected that, even when he broke one of them apart with a stick, though that may have been because the air was heavy with the smell of salt. “The ocean was a little frisky at the time,” he said.

Another beachcomber, Philip Grace, said that he and his wife were walking along the bay last month when they ran across first a scattering of blobs and then many of them. Like Mr. McGrath, he decided to pry one apart.