An unnamed German biathlete has tested positive for a stimulant and Italian bobsleigh athlete William Frullani has also tested positive for a banned substance at the Sochi Winter Olympic Games, according to respective officials on Friday.

A German ski federation official said both of the German athlete's samples tested on Thursday and Friday came back as positive for a stimulant.

"We know who is it but we cannot give a name," the federation's Stefan Schwarzbach said.

"As far as I know it is a stimulant that you sometimes find in extra nutrition."

Earlier, the German Olympic Committee said it had been informed by the International Olympic Committee (IOC) on Thursday evening that a team member had failed a test and a disciplinary commission would convene later in the day after the athlete's B sample was tested.

Frullani, 34,a former track and field athlete, tested positive for the substance dymetylpentylamine, also found in nasal decongestants­, and has left the village.

Italian officials said they had got the green light from the IOC to replace Frullani in their four-man bobsleigh team with the competition set for Sunday.

The IOC said before the Olympic Games it was planning to carry out 2,453 tests during the Games, which is a record for a Winter Olympic Games.