Just hours after reports emerged that she had tested positive for a banned substance, Sachenbacher-Stehle confirmed the news.

“I am experiencing the worst nightmare that you can imagine,” the 33-year-old biathlete said in a statement released through her management on Friday. "I cannot understand how I could have tested positive."

Sachenbacher-Stehle added that she had taken extraordinary steps to ensure that whatever she had put into her body, including nutritional supplements, did not contain banned substances.

"I can only expressly assure everyone concerned that I at no time consciously took forbidden substances and I will be doing everything to have this cleared up completely," she said.

The German Olympic Sports Confederation (DSOB) has since confirmed that Sachenbacher-Stehle has been disqualified from further competition in Sochi and sent home.

Earlier, the spokesman for Germany’s cross-country and biathlon teams said there was reason to believe that the banned substance may have come through something the athlete had eaten.

"It's a stimulant, so it's not EPO or something like that. So there might be a possible explanation that the substance was in an extra nutrition," Scharzbach said.

Sachenbacher-Stehle, 33, has won five Olympic medals in cross country, and barely missed out on her first in biathlon when she finished fourth in the 12.5 kilometer mass start race on Monday.

At the start of the 2006 Winter Olympics in Turin, Sachenbacher-Stehle was handed a five-day suspension at the start due to an abnormally high level of hemoglobin in her blood.

Second doping case

The Sochi Olympics also had a second doping case on Friday, after Italy’s Olympic committee announced that one of its bobsledders, William Frullani had failed a drug test and had been sent home as a result.

It said that Frullani, 34, had tested positive for the substance dymetylpentylamine, which is found in nasal decongestants. He has since left the Olympic village and will be replaced in Italy’s four-man bobsled team, which is to compete on Sunday.

Prior to Friday, there had been no positive doping tests at the Sochi Games.

Ahead of the Olympics, the IOC had announced plans to carry out 2,453 tests during the Games, including 1,269 pre-competition controls in order to prevent cheats from reaching competition.

pfd/dr (Reuters, AP, SID, AFP, dpa)