The World Anti-Doping Agency, the global regulator of drugs in sports, has obtained a digital trove of data that holds the results of thousands of drug tests run on Russian athletes dating back several years. It is considered a final piece of the puzzle revealing the contours of a state-sponsored doping scheme that Russia conducted across multiple Olympics.

The agency said in a news release on Friday that its investigations department was in possession of an electronic file that it believed to contain “all testing data” from January 2012 to August 2015.

The database, fiercely protected by Russian authorities who have been unwilling to share the information with antidoping investigators, did not arrive through official channels but rather from a whistle-blower, according to a person with direct knowledge of the situation who spoke on the condition of anonymity [....]