On Wednesday morning alone, workers from Trelleborg municipality collected more than a thousand of the mysterious sticky spheres, which are slightly larger than a table tennis ball, and made of expanded polystyrene covered with a wax-like substance.
“The municipality has a theory that it might be ballast or packaging material from a cargo ship, but that is just a guess,” Lyudmila Frandsen, an environmental inspector from the municipality, told Sweden's TT newswire.
The first reports of the balls came in at around 10am on Tuesday, after which they have continued to wash up all along the county's south coast.
After scraping off the exterior and breaking open the centre of the balls with a hammer, Frandsen and her team identified the centre of the balls as frigolit, a Swedish variety of expanded polystyrene.
Photo: Johan Nilsson/TT
Hans Karlsson, a professor at the Department of Chemical Engineering at Lund University told the Sydsvenskan newspaper that he believed the balls were used for cleaning mussels and other animal and plant life from the cooling systems in power stations such as Barsebäck, a nearby decommissioned nuclear power station.
“They can look very different and have been used, among other places, at Barsebäck nuclear power station,” he said. “The balls are shot into the inflow and then bounce around in the pipes. They're supposed to be collected up and reused, but if this doesn't work they just get released into the sea.”
One reader, Kristine Persson, wrote in to Sydsvenskan to say that she had been shown similar balls on a tour of the Barsebäck plant this summer.
“The guide said that the balls ofter escaped through broken filters and went out into the sea,” she said. “Many people have found the balls on Barsebäck's beaches over the years.”