An explosion and fire at a Russian facility that handles dangerous diseases like smallpox, anthrax and Ebola has raised safety concerns even as authorities deny any threat.

A gas cannister exploded and started the blaze during renovations on Monday in a decontamination room at the Vector virology and biotechnology state research centre near Novosibirsk, which formerly developed biological weapons.

The building was not damaged and “no work with biological material was being done in the corpus,” the facility said.

A worker was taken to the hospital with burns on 45 per cent of his body and remained there in critical condition, state media reported on Tuesday. Windows were reportedly broken in the blast.

“There can be no panic nor threat,” the mayor of Koltsovo, the research town where the centre is located, told state media, and the emergencies ministry said there was no danger to the population.

But not all local residents were convinced after seeing fire engines racing toward the centre.

“Welcome to the zombie apocalypse,” one posted on a town social media group.