Production at Europe's largest LNG export facility had been halted at the time for the ongoing maintenance work, the company said.
"The leak has been stopped," an Equinor spokesperson told Reuters.
The 54 people that were at the plant when the leak occurred had all been accounted for. It was too early to say whether the incident would cause a delay to future production, the company added.
There were no reports of injuries and no risk to the general population in the area, local police said separately.
In a market message posted on Tuesday afternoon, Equinor said that Hammerfest LNG will be offline until 1200 local time (1000 GMT) on April 26, citing a gas turbine failure. The duration of the outage is subject to revision.
Hammerfest LNG, also known as Melkoeya, has capacity to deliver about 6.5 billion cubic metres (bcm) of gas per year, enough to supply about 6.5 million European homes, and accounts for 5% of all Norwegian gas exports.
Norway is Europe's largest supplier of natural gas after a sharp reduction in Russian deliveries since the start of the war in Ukraine in 2022.
The Melkoeya plant receives its gas via a pipeline from the Snoehvit offshore gas field. Its owners are Equinor, Petoro, TotalEnergies (TTEF.PA), opens new tab, Vaar Energi (VAR.OL), opens new tab and Wintershall Dea.
