Double Olympic champion Charlotte Kalla is to undergo a thorough medical examination after her disappointing start to the International Ski Federation (FIS) Cross-Country World Cup season.
The 29-year-old Swede had high hopes at the start of the campaign but only came 75th over 10 kilometres at the opening leg of the World Cup circuit in Ruka in Finland on Sunday (November 27).
She clocked 30min 56.7sec which was more than four minutes slower than Norway's victor Marit Bjørgen.
She may now miss the next leg of the season in Lillehammer in Norway this weekend.
"In connection with this weekend's World Cup races over 10km classic style in Ruka, Charlotte Kalla felt that something was wrong in the body," a Swedish Ski Association statement said.
"After the races, it was decided, therefore, that she should undergo a thorough medical examination of her state of health."
Only four skiers finished in a slower time in Ruka than Kalla, who won the Olympic 10km freestyle title at Vancouver 2010 and the 4x5km relay gold at Sochi 2014.
"There's something wrong in the body," coach Magnus Ingesson said to NSD.
"She had no fever during the race and she was not aware of damage, but the body did not do as she wished.
"It's one thing if you are in bad shape, this is described as something else, not even close.
"That's what makes it a little puzzling and troubling."