MOSCOW - About 20 people were injured Tuesday night in the southwestern Russian city of Volgograd when a gas cylinder exploded in a cafe, local media reported early Wednesday.

All but three of the injured were hospitalized, with three in serious conditions, local investigators said.

"Cafe visitors and staff were injured. People were hospitalized with burns of 10 to 40 percent of the body," Natalya Kunitskaya, a spokeswoman of the regional investigative department, was quoted as saying by the RIA Novosti news agency.

The gas cylinder exploded Tuesday night in the basement of the cafe, which was located on the ground floor of a three-story building. Following the blast, a fire occurred and engulfed an area of more than 500 square meters in the building.

The fire was put out early Wednesday and residents in the building have been evacuated.

The cause of the explosion remained unknown. Local reports said the gas cylinder had been used to heat the Italian cuisine cafe.

Abnormal cold has struck 60 Russian regions in recent weeks. Businessmen always use additional devices to heat their premises.