- Oops!Something went wrong.Please try again later.
The spill spanned 33 sq miles (85 sq km) in the Gulf of Bothnia region of the Baltic Sea, which separates the two countries.
Since the spill was detected on Wednesday, samples have been taken to find out what the substance is and planes have been flown overhead to gauge how far it has spread.
The coastguard said in a statement: “What the spill consists of is still not clear, but it is not mineral oil, and there is currently no immediate threat of landfall.”
A preliminary investigation into environmental crimes has also been launched.
The coastguard said: “Among other things, it is being investigated which ships have been in the area and what cargoes they have had.”
On Thursday, it said the spill was no longer visible and that spills of substances other than oil had become more prevalent recently.
Jonatan Tholin, head of the coastguard investigation, said in a statement: “New types of fuel are increasingly being transported at sea – biofuel, for instance – and when they come into contact with water they exhibit a great variety of behaviours, which makes it more complicated to quickly establish what substance it is.”
The coastguard said it could not comment on what measures would be taken to deal with the spill until the analysis of the samples was completed next week.