The re-testing of samples from the 2014 Sochi winter Olympics in Russia to identify any cheats who had competed there will last another five years to 2022, the International Olympic Committee has said.
The IOC is re-testing thousands of samples from the Beijing 2008 and London 2012 summer Games as well as the Vancouver 2010 and Sochi winter Olympics to root out any doping offenders.
More than 100 have so far seen their sample test positive from Beijing and London alone, with dozens of medals having been stripped so far.
In addition a total of 28 Russian athletes who took part in Sochi, face disciplinary proceedings over possible manipulation of their urine samples from the Sochi Games.
The IOC had said in December there was "evidence of manipulation of one or more of their urine samples" collected in Sochi.
This follows publication late last year of the second and final part of the World Anti-Doping Agency's independent McLaren report into Russian doping.
It found more than 1,000 Russian competitors in more than 30 sports were involved in an institutional conspiracy to conceal positive drug tests over the course of five years.
"The IOC has an ongoing programme of reanalysis of all stored samples from Sochi, Vancouver and London," an IOC spokesperson said on Tuesday.
"The reanalysis from Sochi of samples from athletes from many different sports and countries will continue through to 2022," the official told Reuters.
"We have no specific timeline. The IOC will continue to communicate on a case by case basis as soon as disciplinary procedures are completed."
The IOC stores samples from past Games for a decade to re-test them at a later date using newer methods or searching for substances that were unknown to anti-doping officials at the time of the competition.
The McLaren report into systematic state-backed doping in Russia over the past years, including during Sochi, has triggered two IOC investigations into the affair and a re-testing of samples.
Russian athletes were partly banned from competing at last year's Rio de Janeiro Olympics while a decision on their participation or not at the 2018 winter Games in South Korea's Pyeongchang has yet to be taken.