Two-time Winter Olympics gold medallist Evi Sachenbacher-Stehle of Germany and Italian bobsleigher William Frullani have been sent home from the Winter Olympics in Sochi after testing positive for banned substances.

Sachenbacher-Stehle was found to have the stimulant methylhexaneamine in her system.

The biathlete, who has five Winter Games medals overall, was tested after finishing fourth in Monday's women's 12.5km mass start race, with both A and B samples failing.

The German Olympic Sports Confederation (DOSB) announced the finding in a statement, which read: "Biathlete Evi Sachenbacher failed a doping test on Monday.

"She tested positive after the mass start race in both the A and the B sample for the stimulant methylhexaneamine."

 Sachenbacher-Stehle, who switched to biathlon from cross country just under two years ago, had her joint-best result of the Games in the mass start, with the 33-year-old also just missing out on a podium place in the mixed relay.

She finished lower down in the women's individual, pursuit and the sprint.

While she had already finished competing, Sachenbacher-Stehle has been excluded from the German team and will fly home on Friday night.

The DOSB statement also confirmed further action rests with the International Biathlon Union (IBU)

Chef de mission Michael Vesper said: "The DOSB represents a doping-free sport and has a zero tolerance policy. We strive for only clean-achieved performance.

"Every doping case is, first of all, a big disappointment. But it is also a proof that the control system works.

"In the run-up to and during the Games we done everything in our power to provide clean sport."

This is not Sachenbacher-Stehle's first run in with the doping authorities as she was banned for five days at the beginning of the 2006 Winter Olympics in Turin due to a high haemoglobin level.

She won her first cross country Olympics gold in the women's relay at Salt Lake City 2002 and her second eight years later in Vancouver.

Sachenbacher-Stehle then decided to compete in biathlon for the 2012/13 season after struggling to continue motivating herself in the cross country, but could now face a lengthy ban after testing positive for methylhexaneamine.

Frullani, who is the brakeman in the four-man bobsleigh team, underwent testing at the Olympic Village on 18 February, where traces of dimethylpentylamine - found in dietary supplements - were discovered.

A statement from the Italian body read: "The athlete requested that the B sample be tested and that was confirmed as positive, leading to his exclusion from the Italian delegation."

Frullani will be replaced in the four-man bobsleigh by reserve Samuele Romanini, with the competition due to get under way on Saturday.