Nikita Kamayev, the executive director of Russian anti-doping agency (RUSADA), said the World Anti-Doping Agency (WADA) was conducting an investigation after one of Pishchalnikova's samples tested positive for an anabolic steroid.

A sample taken two months before the Games reportedly turned out a negative result, but a second analysis conducted after the Olympics showed traces of steroids.

"WADA had asked RUSADA to take a sample from Pishchalnikova," said Kamayev.

"The test had found the presence of a heavy substance [anabolic steroid].

"The test came out positive - it's a fact and now we must wait for the official statement."

Pishchalnikova, who won the 2011 world title in the women's discus in Daegu and finished second at London 2012, had already served a doping ban of two years and nine months from July 2008 to April 2011.

The 27-year-old was among seven leading female Russian athletes found guilty of manipulating drug samples before the 2008 Beijing Olympics.

She also won silver at the 2007 World Championships in Osaka,but was stripped of the medal after the sport's governing body, the International Association of Athletics Federations (IAAF), annulled all her results from May 2007.

"In practice, an athlete who commits a second offence involving [anabolic steroid] could face from eight years to a life ban," said Kamayev.

"As for the Olympic silver medal it depends when her suspension would start if she was found guilty this time."

Darya Pishchalnikova faces losing her Olympic silver medal after a positive drugs test

Pishchalnikova had finished second behind Croatia's Sandra Perkovic at London 2012.

If she is disqualified China's Li Yanfeng will be promoted to the silver medal and Cuban Yareli Barrios to the bronze.

Pishchalnikova would be the third medallist from London 2012 to be stripped of her medal because of drugs.

Nadzeya Ostapchuk of Belarus had her gold in the women's shot put taken away by the International Olympic Committee (IOC) after testing positive for the anabolic steroid metenolone.

And yesterday it was announced that Uzbekistani wrestler Soslan Tigiev had been stripped of his bronze medal because of a positive for methylhexaneamine, a dietary supplement,

Russian Athletics Federation President (VFLA) Valentin Balakhnichev claimed he was shocked by the scandal involving Pishchalnikova.

"Unfortunately, this is not an isolated case," he said.

"We have seen quite enough such cases in Russian sports.

"Still, this is shocking news to me."

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