On March 19, 2008, Russian security services raided TNK-BP offices and detained an employee, Ilya Zaslavsky, on charges of espionage. On March 21, Russia’s environmental agency announced an investigation of TNK-BP’s largest oilfield. The investigation was to be led by the same official that investigated the Sakhalin II project operated by Shell. Shell was later forced to sell a stake in the project to Gazprom. On March 25, the Interior Ministry said it was investigating a $40 million tax evasion case against Sidanco, a former TNK-BP subsidiary.