At least three people have been killed and another five injured in an explosion at a chemical plant in the Irkutsk region in Russia's Siberia.

The Sayansk chemical plant is the largest of its type in Russia and a major overhaul at the site was planned for later this year.

The cause of the incident is still unknown, but early reports suggest a build-up of gases exploded in the furnace.

Officials say the fire was quickly extinguished, helping to avoid an ecological catastrophe in the region.

All the employees have been evacuated from the section damaged by the explosion. However, the work at the plant continues.

A criminal case has been opened into the possible violation of safety regulations.