The explosion at the factory woke up residents of Rouen at around 2:30 am on Thursday
The explosion at the factory woke up residents of Rouen at around 2:30 am on Thursday AFP / Philippe LOPEZ

Firefighters said Friday they have extinguished a huge blaze that broke out at a chemical factory in northern France and forced authorities to close schools and warn of pollution risks for the river Seine.

The fire erupted early Thursday at a storage facility near the city of Rouen owned by Lubrizol, a manufacturer of industrial lubricants and fuel additives that is owned by the billionaire American investor Warren Buffett.

No injuries were reported in the blaze, which sent acrid black smoke billowing over some 22 kilometres (14 miles).

"The fire is out... we are keeping manpower at the site to continue the cooling of all drums," Chris Chislard, a spokesman for the regional fire service, said.

He said some white smoke was still coming from the factory and there was an "unpleasant smell".

More than 200 firefighters were deployed to tackle the blaze at the plant, just a few kilometres from the centre of the city of around 100,000 people.

Lubrizol said the fire damaged a storage facility, a drumming warehouse and an administrative building, and that the cause was still unknown.

It advised residents not to eat fruit or vegetables from gardens without washing them thoroughly, and not to touch the soot or other particles on the ground.

Pierre-Andre Durand, the top regional official, said Thursday that that floating anti-pollution booms had been placed on the Seine due to the risk that fuel or waste water from the site could overflow retention ponds.

Prosecutors have opened an inquiry into the cause of the fire, which began when a booming explosion woke up residents at around 2:30 am (0030 GMT) on Thursday.