A small fire caused a Finnish nuclear reactor to shut down Thursday but 24 hours later the problem was been fixed and the reactor operating again.

The company operating the reactor stated that the small fire was extinguished by staff. The fire had been caused by oil in the turbine bearing, Finnish power company Teollisuuden Voima said.

the reactor had been going under its two-week annual maintenance work this week. It was completed Wednesday and when the accident occurred Thursday, the reactor was operating at 90 per cent of capacity.

Teollisuuden Voima said in a statement that there were no signs “of radiation or environmental impact.” By the end of the weekend, the reactor will operate to full capacity, the operator said.

“The fire was very small, on an area of about a 1 square centimeter (0.16 square inches), but we shut down the reactor immediately to be on the same side,” Reijo Sundell, director of operations at the Olkiluoto plant said. “It posed no danger to anyone,” he added.

The Olkiluoto plant is one of four nuclear reactors operated by Finland. One more is located also in Olkiluoto, while two are at Loviisa. France's Areva and Germany's Siemens began building a fifth reactor, a European Pressurized Water Reactor, at Olkiluoto in 2005.

Olkiluoto is situated 155 miles northwest of the country’s capital, Helsinki.