Norwegian energy company Statoil has about a month to explain how it will address deficiencies that led to a minor oil spill last year, a regulator said.

Statoil reported a release of about 250 barrels of oil during the transfer of products to the oil tanker Hilda Knutsen. Loading of oil from the Statfjord A platform was halted after sheen was reported, through work at the platform itself continued without interruption in October 2015.

Concluding its investigation, the Petroleum Safety Authority of Norway said wind and waves broke down the slick and contributed to the natural dispersion of the released material.

In a letter to the company, the regulator said it has until Oct. 24 to respond with an explanation on how it will handle identified issues that led to the spill.

"The investigation has identified nonconformities related to applying for permission to deploy chemical dispersants and to deficiencies in decision processes and change management," the regulator said.

The PSA in its probe found steel on pipeline walls corroded as a result of the repeated admission of seawater, which broke down its integrity in spots.

In January 2014, Statoil shut down operations at the Statfjord C platform after emergency systems detected an oil leak. More than 250 crewmembers were evacuated to lifeboats but returned to their living quarters later in the day.

The entire Statfjord region is producing an average 80,000 barrels of oil per day.