Russia's anti-doping agency, RUSADA, was suspended in November 2015 after a WADA-commissioned report found evidence of widespread, state-sponsored doping in Russian athletics. Moscow has vehemently denied the allegations.
WADA conditionally reinstated RUSADA in September, but said failure to provide access to the full data from the laboratory by Dec. 31 could lead to another suspension.
Wednesday's visit, which included three WADA delegates, was meant to lay the groundwork for a subsequent mission - on a date not yet announced - to retrieve the data.
"A full technical mission has been provisionally planned but this is subject to a number of outstanding points that need to be clarified in the coming days," WADA said in a statement.
Russian Sports Minister Pavel Kolobkov confirmed that the WADA specialists had been given access to the laboratory but did not say when Russia would hand over the data.
"At this stage it is too early to speak of deadlines and the amounts of work ahead," he said in a statement.
WADA President Craig Reedie told Reuters two weeks ago that the agency had received guarantees that Russia would meet the year-end deadline.
The Moscow anti-doping laboratory was suspended after a 2015 WADA-commissioned report found that its then-director, Grigory Rodchenkov, had been an "aider and abettor" of doping activities and had admitted to having intentionally destroyed 1,417 samples to hinder a WADA audit.
Rodchenkov subsequently gave evidence that did much to expose the extent of the doping, including at the 2014 Sochi Winter Olympics.
The Russian team was banned by the International Olympic Committee (IOC) from competing at this year's Pyeongchang Winter Games over the "systematic manipulation" of doping tests at the Sochi Olympics.
The IOC, however, allowed Russians with no history of doping to compete in Pyeongchang at its invitation as neutral athletes.
(Reporting by Gabrielle Tétrault-Farber; Editing by Kevin Liffey and Toby Davis)
