"It was a technological explosion. The building was partially destroyed," the officials said, adding that at least five people were inside the factory building at the time of the explosion.
"Two people have been rescued from the rubble," he said.
The emergency servicesreported that the entire four-floor building collapsed, adding that 2 people died and 2 more were wounded due to the blast, while one person was still missing.
Following the incident, Governor of the Leningrad Region Aleksandr Drozdenko rushed to the site of the blast.
In the meantime, Russia's Investigative Committee opened a criminal investigation into an explosion.
"A criminal case has been opened over the violation of safety rules at explosion-prone facilities, which resulted in the death of a person by negligence," the committee said in a statement.