Four people were wounded after a gas explosion destroyed part of a five-storey residential building in the Russian city of Naberezhnye Chelny 930 km (580 miles) east of Moscow.
More than 30 people were evacuated from the site, the emergency service said in a report.
Video footage showed the roof and part of two upper floors collapsed, while the lights were still on in other flats in the building.
The flat where the explosion happened was cut off from the gas system in 2010, TASS state news agency reported, citing local gas provider Gazprom Transgas Kazan.
Gas explosions are relatively common in Russia because of ageing infrastructure and poor safety regulations.
In September, a gas blast at a residential building in the Russian city of Noginsk killed two people. Days later, three people were killed in another blast in a Russian village in the Lipetsk region.