TALLINN - A major oil slick, which could contain some 40 tonnes of fuel, has been detected off the coast of Estonia, one week after a cargo vessel sank in the Baltic Sea.
"We have detected a kilometre-long oil slick 4.6 kilometres (2.8 miles) off the Parispea peninsula", on Estonia's northern coast, the border guard said in a statemen.
"Although the pollution is 42 kilometres away from the place where the Runner 4 freighter sank, we have reason to believe the oil slick originates from that vessel," border guard spokeswoman Helena Loorents said Monday.
A lifeboat, two rescue rafts and an emergency buoy from the Runner 4 -- a Dominican Republic-flagged cargo vessel which sank after a collision with another vessel in the frozen Gulf of Finland -- have been recovered near the oil slick.
"An underwater video showed a large crack in the middle part of the ship which proves the story that the contents of one of its fuel tanks has risen to the surface of the sea," Toomas Liidja, a senior inspector with the Environmental Inspectorate, told the Postimees daily.
Up to 40 tonnes of heavy fuel oil may have spilled into the sea, he said.
Border guard officials said the slick was probably smaller that Liidja's estimate.
"Our current estimates show that the slick is not larger than three or four tonnes," Silver Vahtra, head of the border guard's marine pollution department, told reporters.
"But it's very hard to realize the full extent of the pollution as the sea is covered with ice and snow," he said.
"We can presently detect the pollution only in places where there are huge cracks in the ice but we don't know what is under the frozen cover."
The Runner 4, which was carrying a cargo of aluminium, had 102 tonnes of heavy fuel, 35 tonnes of light fuel oil and 600 liters of lubricant oil in its tanks when it sank.
The slick was the second major maritime pollution incident in the Baltic Sea off Estonia since the start of the year.
Ornithologists have estimated that up to 35,000 sea birds may have been killed by an oil slick detected at the end of January, the cause of which still remains unknown.