A guided tour group vanished while exploring Moscow’s underground tunnels during a Sunday downpour Several bodies have been recovered, but the total number of people missing is still unclear

A group of at least five (but possibly more than 20) people disappeared during a heavy rainstorm on Sunday, while on a guided tour of Moscow’s underground water collection system. According to the local media, the known members of the group were the 47-year old manager Dmitry Markushin, his 15-year-old daughter Yelizaveta, their 18-year-old relative Gleb, and Gleb’s girlfriend Victoria.

After the rainstorm, the group stopped responding to messages, and their relatives called the police. According to the Telegram news channels Mash and 112, bodies of two of the teenagers later surfaced in the Moskva River. Baza and Shot report that three bodies have been recovered, though it isn’t yet clear whether they belong to the same people who disappeared while on the excursion.

RIA Novosti reports that an adult man’s body was also found in the water collection system near Moscow’s Paveletsky train station.

It’s still unclear how many people might be missing after descending into the tunnels. According to Baza, 24 people had signed up for that date on a website offering underground excursions through Moscow’s secret underground. According to the website, no tours take place in rainy weather.

Deputy Speaker of the State Duma Boris Chernyshov says that lawmakers should criminalize trespassing at infrastructure facilities like Moscow’s underground tunnels.

The Russian authorities have opened a criminal negligence case. Nikita Dubas, who organized underground excursions and coordinated the guides, has been summoned for questioning. The guide Konstantin Filippov who led the group on Sunday is missing, together with the tour participants.