The head of Russian state-owned energy firm Gazprom has been linked with assets worth $3 billion, a new investigation revealed Thursday.The joint investigation, carried out by media outlet Proekt and a team working with Russian opposition leader Alexei Navalny, found that Gazprom chief Alexei Miller had been in residence at a number of luxurious real estate properties.Many of these properties were held in the names of high-ranking former special services officers, reporters found. Helicopter flight data linked Miller and his partner, Putin’s former secretary Marina Yentaltseva, to an exclusive mansion in Moscow’s Greenfield community. The complex is worth approximately $240 million, making it one of Russia’s most expensive private residences. The mansion’s current owners remain unknown, but until 2020, the building belonged to a company called Vladenie-V.

The firm was formally controlled by two people from the Russian special services: Sergey Tregub from the GRU military intelligence service and Alexander Smirnov from the Federal Security Service (FSB). Vladenie-V received large amounts of money — at least 34 billion rubles [$596 million] — from a Gazprom-owned contractor, Gazstroyprom.

The company also owns a number of luxury cars used by Miller, and the Millerhof palace complex near Moscow, worth an estimated $97.6 million. Journalists also found out that a Cypriot offshore company owned by Tregub’s nephew was used to transfer the money from Gazprom to Vladenie-V.“Gazprom is Putin's Russia in miniature,” Proekt founder Roman Badanin wrote in an op-ed for The Moscow Times Thursday.  “It has become clear that from the very beginning of Putin’s rule Gazprom has been a source of personal wealth for Putin himself; the head of the company, Alexei Miller, who worked as Putin’s secretary for many years; and a group of high-ranking intelligence officers.“The scale of the state money expropriated is shocking.”