Around 140 volunteers in Hanko spent Friday, Saturday and Sunday along the town's long shoreline, cleaning away the white clumps of a yet-to-be confirmed substance that washed up from the sea last week.
On Monday, volunteers were still at work on the shore, if fewer in number, according to Vanessa Ryan, a marine conservation officer at WWF Finland, which organised the cleanup effort.
She said the work that has already been done has reduced the amount of material on the shore, making it less visible than it was over the weekend.
"It was easier to get volunteers then," Ryan told Svenska Yle, the national broadcaster's Swedish-language news unit.
Around four of the town's beaches have already been cleaned up.
On Monday morning, volunteers gathered at the beach adjacent to the Casino restaurant, putting on protective gear and started cleaning.
The cleanup effort is set to continue on Tuesday and Wednesday.
Mixed into the sand
According to Ryan, it has been challenging to completely clean the beaches, particularly the smaller clumps.
"It's very difficult. In some places the clumps are as big as a person's hand. But on other beaches [the material] has broken down and mixed into the sand," Ryan explained, adding that at some point it will be time to accept that it can't all be cleaned up.
Not long after the white clumps began appearing on Hanko's shores, large masses of dead fish also began washing up. There were initial concerns that the white substance may have been behind the fish deaths.
However, a veterinarian's examination of fish samples suggested that the fish had been crushed in a trawler's net.
On Thursday, fuel firm Neste said the white clumps on the shore likely came from the wash water of a vessel transporting cargo for the company.
Neste has vowed to pay for the cleanup, once it is confirmed that the white material actually came from that ship.