It is a huge and horrible mistake

Russian skier Olga Pyleva

Pyleva, who faces a police investigation, won silver in the 15km biathlon on Monday but tested positive for banned stimulant carphedon.

"I was set to retire but I didn't think I'd finish this way," said Pyleva, who has been banned for two years by the International Biathlon Union.

"I beg all my fans, my entire country, to forgive me for the incident."

The 30-year-old has had a glittering career, winning pursuit gold at the 2002 Olympics.

She was also world champion individual biathlete in 2004 and claimed relay world championship golds in 2000, 2001 and 2005.

"I didn't ever wish to put all of my previous achievements and wins in doubt by taking the banned drug," said Pyleva.

"I want to say that I have never intentionally used any banned substances. It is a huge and horrible mistake.

"I hope they believe me. I have always been open. I have spoken only the truth."

The International Olympic Committee (IOC) has handed a file with details of Pyleva's case to an Italian magistrate.

Under the strict Italian anti-doping laws, Pyleva could theoretically face a prison sentence although such an outcome is unlikely.

The IOC says Pyleva will be free to return to Russia, even if criminal charges are bought.

Nikolai Durmanov, the head of Russia's anti-doping committee, said Pyleva's plight was the fault of the company who manufactured and marketed the medication she took for a foot injury.

"Pyleva is not the first athlete who has suffered from their marketing policy," he said.

I was completely sure that the medication was clean

Russia team doctor Nina Vinogradova

"Several other athletes were caught using their drug which contained carphedon.

"We have warned the factory that they were producing doping but they never reacted. They had even recommended their medication for athletes.

"Now we can only express sorrow for the incident. Nothing can be done to improve the situation."

Contrary to statements made on Thursday, which blamed a rogue "unauthorised" doctor for prescribing the medication, Russia team doctor Nina Vinogradova said she had given it to Pyleva in good faith.

"There is not a single word that the medication contains any banned substances in the description that was issued," said Vinogradova, who is considering suing manufacturers Fatherland Medications.

"I was completely sure that the medication was clean.

"We have always been honest and in the last 20 years none of my athletes have been questioned by any anti-doping committee."

But a spokesman for the manufacturers said his company was not at fault and would contest any legal action.

"If a criminal case is filed, we have sufficient facts to show our innocence," said Fatherland Medications strategic planning boss Andrei Belashov.

Nearly 400 drugs tests have been conducted since 31 January, with Pyleva the only athlete to fail.