Finnish police believe the anchor of a Chinese container ship was dislodged and caused damage to the undersea Balticconnector gas pipeline between Finland and Estonia in the Baltic Sea earlier this month.
Finnland's National Bureau of Investigation said it has evidence and data pointing to the Hong Kong-flagged cargo vessel Newnew Polar Bear as the culprit in damaging the pipeline running across the Gulf of Finland.
Detective Superintendent Risto Lohi, NBI's head of the investigation, said in a news conference that a 1.5 to 4-metre-wide dragging trail on the seabed leads to the point of damage in the gas pipeline.
That trail is believed to have been caused by a six-ton anchor which the Finnish navy retrieved late on Monday.
"There are traces in the (anchor) which indicate that it has been in contact with the gas pipeline," Lohi said, citing data from expert analysis.
Whether the pipeline damage was intentional, unintentional or caused by "bad seafaring" is subject of the next phase in the investigation, officials said.
On October 8, Finnish and Estonian gas system operators said they noted an unusual drop in pressure in the pipeline after which they shut down the gas flow.
It turned out that the 77km pipeline that runs between the Finnish coastal town of Inkoo and the Estonian port of Paldiski had been mechanically damaged in the Finnish economic zone and had shifted from its original position where it is buried in the seabed.
Last week, Finnish officials named the Newnew Polar Bear the prime suspect as the course and positioning of the ship coincided with the time and place of the gas pipeline damage.
Recent photos published on social media of the Chinese vessel, which called at the port of St Petersburg in Russia during its Baltic Sea voyage, show the vessel is missing one of its anchors.
The Marine Traffic website shows the ship is sailing in Russian northern waters and is presumably heading back to China via the Northern Sea Route.
Finnish investigators said they have tried several times to contact the ship's captain but without success and are now co-operating with Chinese officials on the case.
A Chinese foreign ministry spokesperson said at a regular government media briefing on Monday that Beijing has called for an "objective, fair and professional" investigation into the damage and stressed the Chinese vessel was sailing normally at the time.
Fresh photos from the Finnish Border Guard showed substantial damage to the 300 million euro ($A500 million) gas pipeline which connects Finland to the European gas network. The Balticconnector pipeline was launched for commercial use at the beginning of 2020.
Repair work is expected to take at least until the end of April.
A Finland-Estonia and Sweden-Estonia telecom cable was damaged at the same time as the pipeline.
Finnish authorities believe the Finland-Estonia data cable damage is tied to the Chinese vessel as well.
with PA