Aerial view of the Cross Country stadium and the Ski Jumping Hill November 23, 2023, in Ruka, Finland. (Photo by Federico Modica/NordicFocus/Getty Images) 
"The concentrations were very low and posed no risk to people or the environment," the Radiation and Nuclear Safety Authority (STUK) said in a statement.
STUK said that the radioactive substances did not originate from Finnish nuclear power plants, though it did not offer an explanation for their detection.
"In many cases, the source of the radioactive substances cannot be identified," the agency said. Finland, Sweden, Russia and the wider region have a number of nuclear power reactors.
(Reporting by Stine Jacobsen, editing by Terje Solsvik)