Tampering of the Moscow Laboratory data carried out by Russia could hamper the prosecution of up to 145 cases stemming from the facility, a report from the World Anti-Doping Agency (WADA) intelligence and investigations (I&I) department has warned.
According to the I&I report, a copy of which has been obtained by the New York Times and Associated Press, the manipulation of the data had "materially prejudiced the ability to pursue" the cases.
A source close to WADA confirmed the figure and told insidethegames some could be salvaged, but many others would fail because of the tampering.
The figure is nearly half of the 298 athletes identified as having the most suspicious samples in the data retrieved from the Moscow Laboratory
WADA claimed in September the 47 cases sent to the relevant International Federations so far were unaffected by claims Russia manipulated the data before it was handed over to the global watchdog in January.
These allegations were substantiated by the I&I during its investigation, while the Compliance Review Committee (CRC) revealed Russian authorities had also fabricated evidence.
Changes had been made to the data after the Executive Committee ordered the country to hand it over as part of the reinstatement criteria for the Russian Anti-Doping Agency (RUSADA), the CRC said.
Reports claim some of these deletions coincided with a WADA team arriving in Moscow in January to retrieve the data, a key tool in building cases against athletes involved in the state-sponsored doping scheme.
The WADA CRC also determined that after November 25 last year, someone in the Moscow Laboratory "planted fabricated evidence into the LIMS database (purported messages between laboratory staff members) to support the argument now being advanced by the Russian authorities that it was Dr. Grigory Rodchenkov and two co-conspirators who falsified entries in the Moscow LIMS database as part of a scheme to extort money from athletes".
The CRC proposed a series of sanctions against Russia - including banning Russia for four years from competing under its own flag at international events, including next year's Olympic Games - as a result of the "extremely serious case of non-compliance".
"Russian athletes and their support personnel may only participate in major events staged in the four-year period where they are able to demonstrate that they are not implicated in any way by the non-compliance," the recommendation adds.
A ban on Russia hosting major events was also recommended by the CRC, whose report will be considered by the WADA Executive Committee during a crunch December 9 meeting in Paris.
The Executive Committee is expected to agree with the recommendation to declare RUSADA non-compliant and will then decide on which measures put forward by the CRC to implement.
Russia will almost certainly appeal any punishment from the WADA Executive Committee to the Court of Arbitration for Sport, which will have the final say on a scandal that is set to overshadow the build-up to Tokyo 2020.