Essex Fire and Rescue Service officials determined that the cause of a July 3 explosion and fire in a grain terminal at the Port of Tilbury in Essex, England was a “dust explosion,” BBC News reported this week. The incident was deemed accidental in nature.

The blast at the Tilbury Grain Terminal blew the top off of a silo and caused a fire in several other grain silos at the site. Firefighters were on scene for 20 days to douse the flames and prevent damage to other parts of the facility, according to the fire service. No injuries were recorded during the response.

“Dust explosions like this are very rare but occur if the dust reaches a flammable temperature,” Essex Fire and Rescue said in a statement printed by the BBC.

Owned by Forth Ports, the Port of Tilbury is the most major port serving London and is the third largest port in the UK.