Russia had its biggest internet outage on Tuesday evening, and conflicting information has emerged about what could have caused the disruptions.

Internet users across the country and abroad were unable to access sites with the .ru domain for hours on Tuesday evening, with the outage affecting hundreds of mobile applications and websites. Radio Svoboda, the Russian service of Radio Free Europe/Radio Liberty, cited experts as saying that the outage was likely the largest in recent history.

The latest large-scale outage came days after Russian media reported localized disruptions in Russia’s Leningrad, Pskov and Novgorod regions.

Russia’s Digital Development Ministry said on Wednesday the outage had been fixed, and that it was caused by technical problems with its Domain Name System Security Extensions (DNSSEC), which strengthens authentication in the Domain Name System using digital signatures based on public key cryptography.