During the Great Purge, Lefortovo prison was used by NKVD for interrogations with torture. Lefortovo was an infamous KGB prison and investigative isolator (Russian: СИЗО, следственный изолятор) in the Soviet Union for detainment of political prisoners.[1] In 1994, it was transferred to the MVD; and, from 1996 to 2005, it was handed back to the FSB, a successor of the KGB. The prison is said to have strict detention conditions.