An investigative report Friday from the international agency that polices drugs in sport put the full scale of the Russian doping controversy into better focus, detailing one of the largest cheating scandals in history and implicating government employees and more than 1,000 Russian athletes who benefited from manipulations to conceal positive doping tests.

The Russian athletes and government officials were involved in an “institutional conspiracy” of an “unprecedented scale,” Richard McLaren, a Canadian lawyer and sports ethics expert who led the investigation for the World Anti-Doping Agency, said at a news conference Friday morning in London. The elaborate doping system and associated coverup began in at least 2011, McLaren said, and continued beyond the Sochi Winter Olympics in 2014.

“It is impossible to know how deep and how far back the conspiracy goes,” McLaren said. “For years, international sports competition has been unknowingly hijacked by the Russians. Coaches and athletes have been playing on an uneven field. Sports fans and spectators have been deceived. It’s time that this stops.”

While the report could intensify calls for Russia to be barred from the 2018 Winter Games in Pyeongchang, South Korea, McLaren said that decision should be made by the International Olympic Committee and the governing bodies of each sport.

The IOC already has established a disciplinary commission to address the Russian doping scandal. The Olympic governing body is in the process of re-examining Russian doping samples collected at the London and Sochi Games. “Professor McLaren’s completed report demonstrates a fundamental attack on the integrity of sport.” IOC President Thomas Bach said Friday in a statement. “As an Olympian, any athlete or official who took part in such a system should be excluded for life from the Olympic Games.”

Friday’s 144-page report confirmed the findings shared in an initial report in July, charging Russian sport and government officials with swapping out the tainted urine samples by athletes with clean samples.

“These athletes were not acting individually but within an organized infrastructure,” he said.

He called the Russian intelligence agents from the FSB — a successor agency to the KGB — “magicians” for being able to crack open tamper-proof bottles and fool doping officials.

“The story of how all the pieces fit together seems like fiction,” McLaren said.

Russian officials pushed back against the report and McLaren’s charges of a widespread systemic doping program.

“The Russian Sports Ministry declares with all responsibility that there are no state programs supporting doping in sport and will continue pursuing a zero-tolerance policy toward doping,” the organization said in a statement.

The report found that the scheme — which was spurred by Russia’s poor showing at the 2010 Winter Olympics in Vancouver — included athletes at the 2012 London Summer Games, the 2013 Universiade Games, the world track and field championships in 2013, and the 2014 Winter Olympics and Paralympics in Sochi, Russia. Among its specific findings:

  • Fifteen Russian medal winners were found to have doped at the London Olympics; 10 have had their medals stripped already.
  • Male DNA was found in the urine samples of two Russian women’s ice hockey players, a sign that those samples were tampered with.
  • Samples provided by two unnamed athletes who won four gold medals in Sochi showed physiologically impossible salt readings.
  • Forty-four bottles containing urine samples from 12 medal-winning athletes had scratches and marks on the inside of the caps, indicating tampering. WADA says this was determined by an unnamed “world recognized expert in firearms and tool marks examinations,” who found that the nominally tamper-proof caps could be removed and then placed back on the bottles without leaving marks visible to the untrained eye.
  • Six winners of 21 Paralympic medals from Sochi were found to have tampered urine samples.

The report also indicated that the systemic doping did not end with the Sochi Games. Russian officials continued swapping out dirty samples monthly at the Moscow testing laboratory for elite summer and winter athletes in 2014, McLaren found.

“The Report, and its evidence published today, shows the scope of subversion; and, focuses on the number of athletes that benefited over a prolonged period of time,” WADA President Craig Reedie said in a statement. “It is alarming to read that 1,000 Russian athletes . . . competing in summer, winter and Paralympic sport — can be identified as being involved in, or benefiting from, manipulations to conceal positive doping tests.”

McLaren found that Russia’s Ministry of Sport helped cover up positive doping results in more than 30 sports in all. Friday’s report did not name the vast majority of the offenders. Their names were instead redacted, but McLaren said their identities have been shared with the governing bodies of each sport, which have the authority to mete out punishments. He said information on 600 summer and 95 winter sports athletes have been forwarded to the international federations of each sport.

“It’s another staggering example of how the Olympic movement has been corrupted and clean athletes robbed by Russia’s state-supported doping system,” Travis Tygart, chief executive of the U.S. Anti-Doping Agency, said in a statement. “The IOC has to act — and clean athletes won’t be satisfied until WADA is empowered to be a truly independent global regulator and the Russian Olympic Committee is suspended until deemed code compliant.”

Even as WADA tried to better police doping and curtail cheats, for years Russia was able to change its practices and stay one step ahead, he said.

“Our investigation has revealed that for every action by WADA, from Russia there was a reaction,” McLaren said.

WADA and IOC officials have been closely scrutinizing recent Olympic results and retesting athletes’ doping samples. More than three dozen medals could be stripped from top finishers at the 2008 Beijing Games, the 2012 London Olympics and the Sochi Games in 2014.

Friday’s revelations encompassed just the second half of McLaren’s investigation. Initial findings were released July 18, barely two weeks before the start of the Summer Olympics in Rio de Janeiro. McLaren then found “beyond a reasonable doubt” that the Russian government ran a widespread doping system and recommended barring all Russian athletes from competing at the Rio Games.

The IOC opted against an outright ban of the country, leaving it up to the individual sports federations to rule on allowing Russian athletes to compete. Opinions varied from sport to sport on how to deal with McLaren’s initial findings, and while more than 100 athletes were forbidden from competing, nearly 300 Russians still participated in the Rio Games.

“I find it difficult to understand why we were not on the same team,” McLaren said Friday. “We should all be working together to end doping in sports. My investigation has gone a long way to bring this dark secret out into the open. Now we must move together and find solutions.”

Patrick Sandusky, a spokesman for the U.S. Olympic Committee, said in a statement: “As we have said consistently, the current anti-doping system is in need of substantial reform. We need to continue to embrace the opportunity to shine a light on bad actors and take the necessary steps to make global anti-doping efforts independent, robust and respected by athletes and fans alike.”

While acknowledging room for improvement, Russian sports and government officials said they were being unfairly targeted and challenged many of the conclusions of McLaren’s initial report. Friday’s follow-up report laid bare the extent of the evidence against Russia, including forensic analysis of past doping samples and emails, documents and other forms of communication. As part of the investigation, McLaren compiled 1,166 documents and pieces of evidence and has made them available on a searchable website.

Friday’s report marked the culmination of high-profile investigation, though probably not the controversy that cast a dark cloud over the run-up to the Rio Olympics. A whistleblower from Russia’s anti-doping agency first approached WADA six years ago with evidence of a state-run doping program. More than five years passed before WADA initiated an investigation, after a German television network aired a documentary based on the whistle-blower’s allegations.

McLaren was tabbed as a special investigator in May following a New York Times report in which Grigory Rodchenkov, a former director of Russia’s anti-doping laboratory in Moscow, outlined Russia’s elaborate doping scheme at the 2014 Sochi Games.

Rodchenkov, who cooperated with WADA investigators, told the Times he tampered with the urine samples of at least 15 medalists from the Sochi Games.

The scope and depth of the scandal could also have an impact on Russia’s ability to stage major international competitions. Russia is hosting the 2018 World Cup, for example. The bobsled and skeleton world championships are scheduled to take place in Sochi in February. Bobsledder Elana Meyers Taylor, a two-time Olympic medalist, has already called for the event to be moved.