Russian sports could face a new wave of doping charges after the World Anti-Doping Agency said Thursday it completed its investigation of a vast trove of evidence on nearly 300 athletes, with nearly half the files showing signs of manipulation.

WADA dug through a computer archive it obtained last year from the Moscow anti-doping laboratory, where past doping cases were covered up. Of the 298 athletes investigated, WADA said it found signs of manipulation in files relating to 145 of them.

Investigators had to contend with deliberate attempts to throw them off the scent, WADA said. Those ruses could still undermine attempts to charge and ban athletes who doped.

It said the athletes investigated came from sports governed by 27 different international federations, but didn't say which.

“The Russian doping crisis has dominated WADA’s time and resources over the past five years and the agency’s investigations team has been on the front line,” WADA president Witold Banka said in a statement. “I would like to thank them for their diligence, professionalism and expertise, as well as the organizations that have now received case packages for the work they will do and their ongoing cooperation in protecting clean sport and for bringing as many cheats to justice as possible.”

After years of bruising legal battles around Russian doping and the 2014 Sochi Olympics, prosecuting the newest cases could be extremely difficult.

WADA has argued the data archive was manipulated while in Russia, with some evidence deleted and false trails laid. That's the basis of an ongoing legal battle to ban Russia's name and flag from the Olympics and other major events for four years.

WADA can appeal if the individual sports bodies choose not to charge athletes based on its evidence. The agency also said it can bring cases directly to the Court of Arbitration for Sport if the relevant federations don't decide on charges within a “reasonable timeframe.”

Separately, WADA has already been re-testing samples which had been stored at the Moscow lab. A total 57 cases are under way based on that analysis.

Russian authorities have strenuously denied there was any state involvement in doping. Instead, Russian law enforcement has sought to paint WADA's star witness, former lab director Grigory Rodchenkov, as a liar who coerced clean athletes into taking drugs.

Russian representatives have also denied any effort to manipulate the data archive. They've suggested that it could have been edited from abroad, or that the database system could have corrupted some files.

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