Chemical plant fire in northern France threatens Seine

Thick black smoke billowed over the northern French town of Rouen on Thursday after a spectacular fire broke out at a chemical factory, forcing authorities to close schools and warn of potential pollution risks for the nearby Seine river.

After hours of battling the blaze, around 200 firefighters had brought it under control by Thursday afternoon, though officials said it could be several days at least before it is fully extinguished.

"The fight they will have to wage to get the situation fully under control will take several days, maybe even weeks," Interior Minister Christophe Castaner said after arriving at the site.

The fire erupted at around 2:30 am (0030 GMT) at a storage facility owned by a Lubrizol, a manufacturer of industrial lubricants and fuel additives.

Castaner said firefighters had managed to remove "the most dangerous products" that could have provoked other explosions at other nearby industrial sites.

But the smoke had spread 22 kilometres (14 miles) and contains "a certain number of compounds which can be a health hazard," Castaner said, though there was no "particular danger" according to initial analyses.

Schools and creches nearby have been shut, and local authorities have asked people living near the factory to stay at home and everyone else to avoid unnecessary journeys.

Prosecutors have opened an inquiry into the cause of the explosion and fire, which work up residents with a booming explosion.

"There was soot all over the streets, pavements and cars," said Jean-Claude Bleuzen, a deputy mayor of Preaux, a town some 15 kilometres northeast of Rouen.

"The smoke is really striking and wherever you are in Rouen you can see it," Marina Andre, a 25-year-old who works in a bar near the factory, told AFP.

"You can smell fuel, not really a burned smell, it's very distinctive," she said, adding that people were still going to work and even cycling near the site of the blaze on the bank of the Seine river.

The factory belongs to US multinational Lubrizol, which is owned by the billionaire American investor Warren Buffett, and sits just a few kilometres from the centre of the city of around 100,000 people.

Pierre-Andre Durand, a top regional official, told reporters that the danger was an overflow of fuel or polluted wastewater from the site into the river.

The Seine, one of France's biggest rivers, flows through Paris to the south and empties into the English Channel further north in Le Havre, which is home to a major fishing fleet.

In January 2013, the Lubrizol factory was responsible for a giant leak of the gas mercaptan, which smells like cabbage or rotten eggs and is often added to natural gas to alert people in case of leaks.

A cloud of the gas blew all the way to Paris and across the Channel into southern England, where residents complained about the odour.

And in 2015, 2,000 litres of mineral oil, which is used in lubricants, leaked from the Lubrizol site into the local sewer system in Rouen, which is famed for its cathedral.

"The biggest priority is to protect the most risky parts of the factory, which could explode and then create a domino effect of other fires," Jean-Yves Lagalle, the head of firefighting in the region, told reporters.