Athletics' governing body has admitted that Dwain Chambers' revelations to BBC Sport could see the sprinter lose all his medals from 2002 onwards.
Chambers told the BBC that he had used the steroid THG from the start of 2002 - 18 months before he was caught.
Istvan Gyulai of the International Association of Athletics said: "There will be a further investigation.
"An athlete who admits to having used drugs can, for eight years after it happened, have his results annulled."
Chambers won European 100m gold in 2002 and followed that with another gold as part of the 4x100m relay team.
But he could now see those results scratched - which could mean that his Great Britain relay team-mates Christian Malcolm, Marlon Devonish and Darren Campbell also lose their golds.
Chambers could also have his British record of 9.87 seconds, which he ran in September 2002, annulled.
He tested positive for THG in August 2003, a result which cost the same relay squad their silver medals from the World Championships that year.
Gyulai, who has requested a copy of the BBC's interview with Chambers, said: "We have to check from the legal point of view if this is an admission or not.
"Dwain is saying he took it, but had no idea it was prohibited.
"But if this is an admission, all his results from when he said he started taking it will have to be annulled."
European Athletics Association president Hansjorg Wirtz echoed Gyulai's comments.
He said: "The EAA has a zero-tolerance policy on doping.
"We abide by IAAF rules, so we will follow the lead from the IAAF in regard to any possible annulment of the results of Chambers."
The GB men's team could even be stripped of the European Cup which they won in Annecy in June 2002.
Britain won the competition by just four points, with Chambers' win in the 100m contributing eight points to that overall tally.
David Moorcroft, chief executive of UK Athletics, promised to study the BBC's interview with Chambers.
He said: "I look forward to working with the IAAF and EAA on the implications of championship medals and records set by Chambers."
The precedents for Chambers are not encouraging.
Ben Johnson tested positive for steroids at the 1988 Olympics, but when he later admitted taking banned drugs earlier in his career, he was stripped of the world record that he had set a year earlier in 1987.