MOSCOW (Reuters) - Russian investigators on Wednesday detained three managers of an Arctic power station in connection with a huge fuel spill last month, as wind, rain and cold complicated the clean-up.

The federal Investigative Committee said it was still examining the cause of the spill on May 29 at an Arctic power station in Norilsk, home to Norilsk Nickel, the world's leading nickel and palladium producer.

Some 21,000 tonnes of diesel - the volume of 10 Olympic-size swimming pools - leaked into rivers and subsoil in an incident that Greenpeace compared to the 1989 Exxon Valdez oil spill off Alaska.

Investigators said in statement that they had detained the head of the power station and the chief engineer and his deputy, whom they suspected of continuing to use an unsafe storage tank that had needed major repairs since 2018.

Roman Vilfand, head of science at the weather forecaster Hydrometcentre, said bad weather was hampering the clean-up operation, the RIA news agency reported.

Strong winds, which were threatening to push fuel over containment barriers on a river, were expected to last two days, Vilfand said.

Nornickel said on June 2 that it expected to be able to draw off the fuel from the river within 10-14 days.

The emergencies ministry said it had been provided with satellite data on the spill from 14 foreign satellites, the Interfax news agency reported.

Nornickel has said the accident was caused by a thaw in the permafrost weakening the foundations of the storage tank.

It said the detention of the managers was overly harsh.

"There is no reason to believe that our colleagues could interfere with the investigation," Nornickel said. "The power station managers are working with law enforcement officials, and would be much more useful on the clean-up site."

(Reporting by Polina Devitt and Anastasia Lyrchikova; Editing by Kevin Liffey)