According to Reuters reports, a fire and explosion at a Sibur petrochemicals plant in Russia’s Tatarstan region on March 31 killed at least three people, including a firefighter, and injured dozens.

Sibur said two employees died and 68 people were injured.

Twenty-one remain in hospital, with three in serious condition.

One firefighter also died after a nearby explosion.

The company said a gas mixture exploded after a pressure loss at a synthetic rubber and plastics unit.

The cause of ignition is still under investigation.

 Firefighters brought the blaze under control, and there was no risk of further spread. Authorities are checking air quality and said no environmental threat has been detected.

Local reports said several nearby apartment windows were damaged by the blast.