Uniper SE's oil-fired power plant in Sweden experienced a partial power failure on Thursday morning, which could affect the stability of power supplies at a time when they are needed the most.

There was a boiler trip in one of the Karlshamn plant's units. Heavy fuel oil is burned at the facility.

The German energy giant said on Tuesday that the plant had been operating frequently from morning to night to increase supplies in the south of Sweden.

The power prices are soaring that Sweden is turning to burning oil.

Nuclear outages and a lack of wind generation sent prices in that part of the country to a record. The power went up to as high as 540.47 euros a megawatt-hour on Wednesday.

In the filing, Uniper didn't give any information on when the unit would return. The firm doesn't have to report exactly which hours the plant is running.