"The criminal case on the fact of an explosion in one of the cafes in St. Petersburg was transferred for further investigation to the central office of the Investigative Committee of Russia," the department said in a statement.
Investigators and criminologists are working at the scene.
The course of the investigation was put under control by the head of the IC Alexander Bastrykin.
The Ministry of Health of Russia previously clarified that the number of victims of the explosion in a cafe in St. Petersburg increased to 32. According to the latest data, eight people are in hospitals in serious condition.
On April 2, an explosion occurred in St. Petersburg. The incident occurred in the café "Street Bar" on the University Embankment in the city center. Voenkor Vladlen Tatarsky was killed.