Scientists at Russia’s top nuclear research facility were detained for allegedly mining bitcoin, BBC reported on Friday. It is unclear when the crime had taken place or how many suspects were involved.

The engineers at the Federal Nuclear Centre in Sarov had tried to use one of Russia’s most powerful supercomputers to mine bitcoins, reports said. “There has been an unsanctioned attempt to use computer facilities for private purposes including so-called mining,” the press service of the centre said, according to BBC. A criminal case has been filed against them, the centre said.

Sarov is a closed city in Russia about 400 km from Moscow. The city’s inhabitants are subject to travel restrictions. The centre houses Russia’s most powerful supercomputers, which are cut off from the internet.

The mining comes at a time when the government in Russia is working on its first cryptocurrency legislation to regulate mining, initial coin offerings, and cryptocurrency trade.