The cause of the spill was dredging work which disturbed existing, old fuel residues, spreading pollution to the Noblessner Harbor, a popular and gentrified area of Tallinn, and also to nearby spots used by those who like to go ice swimming.

Despite the spread of the pollution, no authority had issued public warnings when "Aktuaalne kaamera" reported on the case.

Tarmo Tehva, head of the Harju and Rapla counties supervisory bureau at the Environmental Board (Keskkonnaamet), said his authority was awaiting a press release from the Estonian Navy (Merevägi).

He said: "Since we have been in discussions with the Navy, and they are expected to prepare their own press release explaining what is happening there, what work has been carried out, and how the pollution happened during these operations, the Environmental Board has not yet issued a statement."

Tehva added the authority could have notified the public of the slick, which first appeared last Wednesday, February 12, on Tuesday of this week.

"We could have provided the public with a more immediate explanation about the work being carried out at the naval harbor, why it is necessary, how the pollution occurred, and that every effort is being made to remove it," Tehva added.

Noblessner, west of the main ferry harbor in Tallinn Bay, is close by the navy's Miinisadam harbor.

Dredging operations in the naval harbor last week likely disturbed oil residues dating back to the Soviet era.

Though the zone was cordoned off and requirements seemingly met, strong winds caused the oil slick to spread.

Märt Lepik, the founder of Lennusulps, a winter swimming enthusiasts' club, said querying the origins of the slick had been met with denials.

In any case, winter swimming was off as soon as Lepik was made aware of the situation this week.

"When we tried to get information today about the suspected location of the pollution, i.e., the naval harbor, they told us they knew nothing about it either. As of now, we have no idea when swimming will be possible again," Lepik said.

The thin layer of oil on the mostly unfrozen surface water can currently be seen in several harbors in Tallinn, not only Noblessner and Miinisadam naval harbor, but also Katariina Quay, and at multiple winter swimming spots. Katariina Quay is adjacent to the Pikakari beach on the Kopli peninsula.

Cleanup efforts are ongoing, while depending on weather conditions, the pollution should be removed by the end of the week, "Aktuaalne kaamera" reported.

The dredging work which caused the slick is to continue, however, meaning additional oil residues are expected to surface.

"More pollution will certainly surface when the contaminated seabed is disturbed again. These operations are still ahead of us," Tehva noted.

The pollution had not harmed local wildlife, he went on.

"As far as we know, this has not caused any major threat to wildlife. We are monitoring the birds in the area, and so far, we have not observed any contamination. In terms of hazard, this is an oil product, but just a thin film of it on the water's surface does not pose a direct threat to people."

"However, swimming in an oil slick is definitely not to be recommended," Tehva explained.

Despite all this, the authorities did not, at the time the report was filed, plan to install any warning signs, leaving winter swimmers and local residents potentially unaware of the hazard or reliant on word of mouth, media reports, and social media posts.

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