At least 10 workers have died in southern Russia after inhaling toxic fumes while cleaning sewers.
The accident occurred at a sewage treatment plant in the village of Dmitriadovka, near Taganrog, on Friday.
Local authorities in the city in Rostov Oblast confirmed that at least 10 people have died, and eight others are hospitalised.
Taganrog confirmed in a statement that an emergency had happened at a "pumping station of raw sludge" on Friday morning.
"Investigative bodies and all instant response services are working at the scene of the incident," they added.
Russia's Investigative Committee reported that the casualties worked for the Municipal Unitary Enterprise "Management of Vodokanal" and that bodies were still being recovered from the scene.
Regional authorities have blamed methane, a gas resulting from the decomposition of human and organic waste. Fatal accidents due to non-compliance with safety standards or aging infrastructure are common in Russia.
"There are no exact answers to questions about the causes of the tragedy," said Inna Titarenko, Chairman of the Taganrog Duma.
"What happened today is a real misfortune that has not happened before in Taganrog. On behalf of the city, I express my deep condolences, sympathy, and support to all the relatives of the victims."