Norway's Accident Investigation Board said a towboat was also involved in the accident, but didn't say how.
The circumstances of the accident, which took place shortly after 4 a.m. (0300 GMT) in the Hjeltefjord near Bergen, are not yet clear. The collision is believed to have happened when the vessel was leaving Sture Terminal, 50 kilometers northwest of Bergen, carrying 625,000 liters of crude oil.
Equinor confirmed early this morning that personnel at Sture "without emergency tasks" will be evacuated and that a shutdown will be performed as "a precautionary measure". As a result of shutting down the pipeline, the Kollsnes plant also had to cease operation.
Stensoenes said the ship was "strongly listing" - or leaning to one side - and that it had been pushed by towboats into shallow water, where it can not fully sink.
This incident will mean reduced gas deliveries to continental Europe.
Norway is the biggest oil producer in Western Europe. "The market was already quite bullish due to lower temperatures", a British gas trader said.
Norway's Accident Investigation Board says the Marine Safety Investigation Unit of Malta will participate in the investigation into the cause of the collision as the tanker -returning to port for inspection- is Maltese-registered.
The 62,000-tonne tanker received only slight damage and is waiting to be towed to a nearby oil terminal, the rescue center official said.
The Sture oil terminal, which has about 6 million barrels of underground oil storage capacity, is the receiving terminal for Oseberg Blend (105,000 bpd impacted) and Grane Blend (260,000 bpd impacted).
Oseberg is one of the crude streams underpinning the global Brent oil benchmark.
Production at the Edvard Grieg field was shut on Thursday, a source with knowledge of its operations said.
The Sola TS, an Aframax class vessel built in 2017, belongs to Tsakos Energy Navigation, the company's website says.