Austrian cross-country skier Johannes Duerr was kicked out of the Sochi Games after testing positive for the blood booster EPO.
It is the fifth doping case, and most serious so far, at the Olympics.
"It is a black day for us" Austrian Olympic Committee President Karl Stoss said at a news conference on the final day of the Games.
I am in a way glad it has come to an end... This is the worst thing I've done in my life.
Duerr finished eighth in the men's skiathlon 9th February and was tested seven days later in Austria, where he had flown back for training.
He returned to Sochi and had been due to compete in the 50-kilometer mass start, the final cross-country event.
Stoss said the team was "shocked" by what happened, adding Duerr was tested 14 times before this season, all the results negative.
He said the skier's accreditation was pulled and he was on his way home.
At the airport in Sochi, Duerr was remorseful. He told Austrian TV he can "only apologise to everyone."
"So many people have been doing all they could to help me and now I've disappointed them with my silliness" he said, adding he is not sure what awaits him.
"I am not afraid" he said. "I am in a way glad it has come to an end... This is the worst thing I've done in my life. This is very, very tough. You can't explain this in three sentences."
EPO is used to boost red blood cells that carry oxygen to the muscles, increasing stamina and endurance.
The four other cases involved minor stimulants that can be found in food supplements.
None of the five athletes won medals in Sochi. The other four were: Latvian hockey player Vitalijs Pavlovs, Ukrainian cross-country skier Marina Lisogor, German biathlete Evi Sachenbacher-Stehle and Italian bobsledder William Frullani.
The Austrian cross-country and biathlon teams were at the centre of a major doping scandal at the 2006 Turin Olympics. Italian police, acting on a tip, raided the team lodgings and seized blood doping equipment and other substances.
New generation tarnished
No Austrians tested positive at those games, but several were later banned for life by the International Olympic Committee.
The IOC fined the Austrian Olympic Committee $1 million, and the Austrian ski federation cut funding for
biathlon and cross-country for several years.
The 26-year-old Duerr has been the leading athlete in a new generation of cross-country skiers attempting to rebuild the sport's image in Austria.
He debuted on the World Cup circuit in 2011 and finished third in this season's overall Tour de Ski standings.
The IOC is conducting 2,453 drug tests in Sochi, a record for the Winter Games and also stores doping samples for 10 years to allow for retesting when new methods become available.
There was only one positive test at the previous Winter Olympics four years ago in Vancouver.
Backstrom allergy medication
Sweden centre Nicklas Backstrom failed a doping test for a substance found in an allergy medication and was withdrawn from the big hockey final.
"I got the message two hours before the game that something was wrong'' Sweden coach Par Marts said after his team lost 3-0 to Canada in the gold medal game.
Backstrom, who plays for the Washington Capitals in the NHL, was scratched just before the game began.
Backstrom is the sixth athlete to fail a doping test at the games.
Five of the six, including Backstrom, tested positive for minor stimulants that are often found in food supplements.