Along the beaches on Väddö are fist-sized lumps of sticky pine oil.
The rescue service and the Coast Guard have inspected the coastal stretch and can state that a stretch of about 40 km is affected.
The oil probably comes from a ship that has cleaned its tanks out at sea.
- The spill probably took place a month ago at the same time as the ice settled, which caused the oil to clump together.
Now that the ice is melting, the lumps are blowing ashore, says Charlotta Tillberg, acting director of safety and security at Norrtälje municipality.
No crime
Tall oil is biodegradable and it is therefore not illegal to discharge it into the sea.
Norrtälje municipality has therefore chosen not to make any police reports of environmental crimes.
- We will send out staff to clean up and we gratefully accept tips from the public if you see areas that are badly affected, says Charlotta Tillberg.
Norrtälje municipality appeals via its website for the public's help to pick up the tall oil.
The municipality writes that it is possible to throw the lumps in their own rubbish bin.
Larger vessels will also be located at the fire station in Älmsta where you can leave your waste.