Tragedy marked the end of the annual World Sauna Championships in Finland. One of the finalists died, the organisers said.
Both Russian finalist Vladimir Ladyzhensky and Finnish rival Timo Kaukonen were taken to hospital after collapsing and Ladyzhensky later died.
The event has been running since 1999. It requires participants to withstand 110C for as long as possible.
The competition took place in Heinola, 138km (86 miles) north of Helsinki.
All the rules of the event have been followed, said its chief organiser.
In a statement, organiser Ossi Arvela said that the organisers were grief stricken at the events.
Arvela added that the police were already at the venue and were undertaking an investigation.
He said: “All the rules were followed and there was enough first aid personnel. All the competitors needed to sign in to the competition with a doctor’s certificate.”
Kaukonen was last year’s champion. He is still being treated in hospital at the city of Lahti.
News wires released still pictures from the event showing the pair being treated after having collapsed, apparently suffering burns.