The Russian news agency "TASS" announced on Monday that four bodies have been discovered in Moscow's sewage system, with more individuals still missing after being trapped due to heavy rainfall during an underground tour. Moscow Mayor Sergei Sobyanin described the incident as a "horrific tragedy" without specifying the number of victims. He stated that the search for the missing is ongoing and that investigators are looking into the details of what occurred. TASS reported that the authorities have initiated a criminal case and are interrogating the organizers of the tour, which has been described as illegal. The Russian media outlet reported that a total of eight people were participating in the tour. Rescue personnel stated that the heavy rain in Moscow on Sunday caused a sharp rise in the water levels in the sewage system, preventing individuals from escaping to the surface. Several guides offer tours of the extensive sewage network in Moscow, with parts dating back to the 19th century.