A state-directed cheating programme in Russian sport resulted in no fewer than 312 positive results for doping being withheld, an inquiry has found.
Investigator Richard McLaren said the programme, which he dubbed "disappearing positive methodology", covered 28 sports and lasted from 2011 until at least last year's world swimming championships.
But he did not make any recommendations for the future of the Russian team at the Rio Olympics, saying it is up to others, including the International Olympic Committee, to "absorb and act upon" his 97-page report.
IOC president Thomas Bach immediately called the findings a "shocking and unprecedented attack on the integrity of sports and on the Olympic Games", and said the committee will not hesitate to apply the toughest sanctions available against those accused of cheating.
The IOC executive board will meet on Tuesday to begin discussing its options.
McLaren said allegations made by Moscow's former anti-doping lab director about sample switching at the Sochi Olympics went much as described in a New York Times expose story in May. That programme involved the switching of dirty samples with clean ones and prevented Russian athletes, including more than a dozen medal winners, from testing positive.
But McLaren said the cheating began in 2011, shortly after Russia's disappointing performance at the Vancouver Olympics. It included the 2013 track world championships in Moscow and was in place during the 2015 swimming world championships in Kazan.
In short, Russia's deputy minister of sports, who was also part of Russia's Olympic Committee, would direct workers at Moscow's anti-doping laboratory on which positive samples to send through and which to hold back. Assisting the plan was Russia's national security service the FSB.
McLaren said out of 577 positive sample screenings, 312 positive results were held back - or labelled "Save'" by the lab workers - but that was only a "small slice" of the data that could have been examined.
More than 240 of the 312 "Saves" came from track and field and wrestling, but other sports involved included swimming, rowing, snowboarding - and even table tennis.
McLaren suggested the numbers could have been higher, but he had only 57 days for his investigation, which was commissioned by the World Anti-Doping Agency after the Times story came out.
Time is crucial because the Olympics begin on August 5, and decisions about Russia's participation in Rio must be made.
The US Anti-Doping Agency (USADA) is one of several sport organisations that said it would call for a full ban of the Russian team if the report showed evidence of a widespread, state-sponsored doping conspiracy. McLaren's report said it did, and the investigator said he was "unwaveringly confident in my report".
USADA chief Travis Tygart said the report "concluded, beyond a reasonable doubt, a mind-blowing level of corruption within both Russian sport and government that goes right to the field of play".
He urged the international community to come together to ensure that what he called an unprecedented level of criminality never threatens sports again.
Following publication of the McLaren report, the World Anti-Doping Agency's executive board said it wants the IOC to ban all Russian teams from the Rio Games.