A new report from the World Anti-Doping Agency examined the scale of the operation
Over 1,000 Russian athletes in 30 summer and winter Olympic and Paralympic sports benefited from a systematic cover-up of doping, including London 2012 medalists.
An independent investigation established positive drugs tests were concealed at the London 2012 and Sochi 2014 Olympics and the 2013 World Athletics Championships The athletes under suspicion include 503 summer sports competitors and 92 winter athletes.
The investigation, led by Canadian Professor Richard McClaren found "an institutional conspiracy across winter and summer sports athletes who participated with Russian officials within the Ministry of Sport ... along with the FSB [Russia's security service] for the purpose of manipulating doping controls."
These included 15 medalists from the London 2012 Games and two Sochi athletes who won four gold medals.
Six winners of Sochi 2014 Paralympic medals were found to have samples tampered with.
Professor McClaren published evidence of how supposedly secure bottles were tampered with, and dirty samples replaced with clean urine that in some cases contained mixed DNA, and some samples that were "physiologically impossible". In one case, samples supposed to belong to two female ice hockey players were found to contain male DNA.
The investigations examined allegations from the former Moscow anti-doping laboratory director that dirty samples given by drug-using Russian athletes were replaced with clean urine in order to avoid detection.
In Sochi this involved a sophisticated operation by the FSB, whereby they developed a system to remove the supposedly "tamper-proof" sample bottles, and drilled a hole in the wall to pass bottles into the official anti-doping laboratory.
Analysis of the samples and sample bottles revealed the extent and sophistication of the doping system.
Investigators recreated the technique for opening the bottles using a metal probe that lifted a safety catch, but left tell-tale scratches and marks.
This provided "conclusive proof" that bottles that had been tampered with, supported by analysis of the samples given by athletes. Investigators found examples of DNA that did not match the athlete it was supposed to belong to, or mixed DNA.
This included mixed DNA in the same bottle from more than one man, more than one woman, and mixed male and female DNA.
They also found that salt and even coffee granules had been added to clean samples to recreate the physical constituents of the dirty samples that were replaced.
Investigators established Sochi medalists whose urine samples contained such high levels of salt that it was physiologically impossible levels for a human to have passed them.
There were also some with such low levels of salt it was physiologically impossible for a human to have passed.
The investigators have also published emails from the Russian Ministry of Sport instructing officials to "save" specific athletes who tested positive, and not protect others.