Some 110,000 litres of oily water leaked from a tank at a national security contingency storage facility into a river leading in the Oulujärvi Lake.
At the time, the spill of oil was estimated at around 1,000 litres. However, it is now estimated some 20,000 litres have leaked from the warehouse affecting beaches beyond oil booms.
Oil supplier Neste is responsible for repairs and oil clean-up operations. The company is dispatching additional equipment from southern Finland to help in the clean-up.