Emergency officials in Moscow are urging residents in certain areas to stay inside as a noxious gas makes it way through the Russian capital.
The cause of the gas is unknown, the BBC reports. No chemical factories in the area have yet reported any accidents. Local media reports suggest the gas is hydrogen sulphide, which can be very toxic and whose smell resembles rotten eggs.
The gas has been detected in the eastern, south-eastern and central parts of the city, as well as in certain shopping districts and around a government building.