BORDEAUX (AFP) - An explosion on Wednesday (Aug 3) in a French factory producing a compound used in gunpowder injured eight people, one of them seriously, officials said.

The blast occurred in a building at the Manuco factory in Bergerac, in the southwestern Dordogne region, which makes nitrocellulose, a highly flammable compound used for ammunition.

The factory is qualified as "high threshold" under the EU Seveso classifications for chemical sites, a category considered high-risk in the event of an industrial accident.

The cause of the blast was not yet known, authorities said.

Local official Jean-Charles Jobart said the building where the explosion happened contained around two tonnes of nitrocellulose.

Around 40 people were present in the factory at the time.

Authorities reported fire and smoke at the building, which was quickly cordoned off.

Five ambulances, two helicopters and around 50 firefighters were dispatched to the site, and the local hospital put on alert.

Manuco was taken over last year by Eurenco, which describes itself as the leading European manufacturer of gunpowder and explosives.