A Moscow sewer overflowing on August 15, 2016. VASILY MAXIMOV/AFP VIA GETTY IMAGES

Five people were found dead and several others were missing after heavy rains trapped participants on a tour of Moscow's sewer system, state media reported Monday.

The TASS news agency said water levels in the sewers rose rapidly after a downpour and the victims were couldn't escape to the surface.

"The death of five participants to the illegal excursion has been confirmed," the emergency services were cited as saying.

Video shared on social media showed investigators looking down a manhole in the capital, while divers searched the Moskva river.

Several tour operators offer trips into the vast tunnels of the Russian capital's sewer system, some of which were constructed during the 19th century, though it wasn't clear if all the visits are permitted by authorities.

Daniil Davydov, described as an "urban explorer," told the RIA news agency that there were shelters in the tunnel where people could escape but that nobody could be found.

"I hoped that maybe I would still be able to find some survivors there. There are two shelter points, but there was no one there," he said.

Police have opened a criminal investigation into the organiZer of the tour, local media said.

Source