Olympic authorities are to look into possible doping offences in cycling at past Games following recent admissions by former riders of the Telekom team.
Riis admitted using EPO when he won the Tour de France in 1996
Bjarne Riis, the 1996 Tour de France winner, Erik Zabel, Rolf Aldag and Christian Henn have all admitted using banned blood booster EPO.
The International Olympic Committee said it found the revelations "disappointing and concerning".
Henn won a bronze medal in the road race at the 1988 Seoul Olympics.
The probe could put further scrutiny on Jan Ullrich, the 1997 Tour de France champion who won the Olympic gold medal in the road race and silver in the time trial at the 2000 Sydney Games.
Ullrich, who won the Tour de France with Telekom, retired in February after being implicated in the Operation Puerto doping scandal in Spain. He has, however, denied any wrongdoing.
It would be shocking to have Riis included in the Tour de France
Meanwhile, Tour de France director Christian Prudhomme said Riis would not be welcome at this year's tour.
Riis, who is sporting director of the CSC team, left Ivan Basso out of the 2006 Tour because of suspicions hanging over the Italian rider in the wake of the Operation Puerto affair.
"We have the right to challenge whichever rider or team official we want to," said Prudhomme.
"We are speaking with teams and sponsors but, at this time, it would be shocking to have Riis included in the Tour de France.
"It would be logical that Riis applies to himself the same treatment that he applied to Ivan Basso last year."