MOSCOW — The Russian equivalent of the F.B.I. said on Wednesday that it had found evidence rebutting the accusations of systematic doping raised by a whistle-blower who coordinated drug testing during the 2014 Winter Olympics in Sochi.

Russia’s Investigative Committee said in a statement that it had obtained documents relating to the doping samples of 15 Russian athletes who were recently banned for life from the Olympic Games, following revelations that their urine samples had been surreptitiously tampered with overnight in Sochi to conceal the use of banned, performance-enhancing drugs.

Those documents, the committee said, stated that doping samples “were delivered to the Sochi laboratory in the daytime, were registered within 30 minutes to two hours and were later transferred for analysis.”

Grigory Rodchenkov, the head of the Sochi laboratory during the 2014 Winter Olympics, has said that he managed a very different process, working nightly at the Games to substitute incriminating samples before they were analyzed.