A fire caused by a gas explosion has torn through a Russian laboratory that houses viruses including smallpox, Ebola and HIV.

Russia claims there is no sustained threat after a gas cylinder exploded on the fifth floor of the State Research Centre of Virology and Biotechnology, known as Vector.

Located in Koltsovo, in the Novosibirsk region of Siberia, the site was a nexus for biological warfare development during the Soviet era.

The State Research Centre of Virology and Biotechnology, known as Vector (pictured), released a statement yesterday saying a gas cylinder exploded on the fifth floor

One worker was left with second and third degree burns and had to be taken to hospital after the blast, which blew out the windows at the facility.

Vector is one of two places in the world where the smallpox disease is stored, the other is at a high-security laboratory - the US centre for Disease Control in Atlanta.

According to RT, authorities scrambled 13 fire engines and 38 firefighters to tackle the blaze - which the lab claims covered 30 square metres.

The mayor of Koltsovo has claimed that no biologically hazardous materials were released in the explosion.

Vector is one of two places in the world where the smallpox disease is stored, the other is at a high-security laboratory - the US centre for Disease Control in Atlanta

In 2004 a lab worker, Antonina Presnyakova, at Vector died after she accidentally pricked herself with a needle which contained the Ebola virus.

An investigation has been launched to find the cause of the explosion.

The last naturally occurring case of smallpox was in 1977 and by 1980 the World Health Organisation had declared it globally eradicated.

Smallpox is estimated to have killed up to 300million people in the 20th century.