SOCHI (AFP) - The first doping cases to hit the 2014 Sochi Games emerged Friday after a double gold-medal winning German female biathlete and an Italian bobsledder tested positive for banned substances.

German biathlete Evi Sachenbacher-Stehle, who has won two gold medals at previous Olympic Games, confirmed she had tasted positive, describing it as the "worst nightmare you can imagine".

Meanwhile, the Italian Olympic Committee said Italian bobsledder William Frullani had tested positive for a banned substance and had already been kicked out of the Sochi Games.

The news that a well known athlete as Ms Sachenbacher-Stehle has failed a doping test has caused shock waves in Germany, which for years has prided itself on its tough anti-doping fight.

"I cannot explain how this positive doping test came about," Ms Sachenbacher-Stehle said in a statement, adding that she had had all her dietary supplements tested in a laboratory.

Reports said that the positive test - carried out on February 17 - may have come about due to contamination from imported energy bars.

"I am living through the worst nightmare that you can imagine," she added. "I can only assure everyone that I have never knowingly taken a banned substance and will do everything to clear this up so there are no questions," she added.

Mr Frullani, 34, tested positive on February 18 for the banned substance dymetylpentylamine. He has been replaced in the Italian four-man bobsleigh team by Samuele Romanini.