Some 900 tonnes of lithium batteries were on fire at a battery recycling plant in southern France, authorities said on Sunday, sending a cloud of thick black smoke into the sky above the site.

The fire broke out on Saturday in a warehouse owned by French recycling group SNAM in Viviez, north of Toulouse, local councillor Pascal Mazet said in a statement on X.

Lithium batteries are vital in electrical devices from phones to electric cars, but contain combustible materials which, combined with the energy they store, can make them vulnerable to catching fire when exposed to heat - a potential danger given the toxic materials their burning can emit.

In January 2023, a large fire broke out in a Normandy warehouse storing car components and thousands of lithium batteries, which was brought under control without causing any casualties. Firefighters said there were no indications of the release of dangerous air pollution.

French media showed thick smoke over the Viviez site and newspaper Le Monde reported that up to 70 firefighters were battling to get the fire under control.

Charles Giusti, a local official in the Aveyron prefecture which includes Viviez, said on BFM television there was no danger to people living nearby.

The prefecture said in a statement overnight that while the fire was under control, it was burning slowly and was expected to last for several hours.

SNAM did not immediately respond to a request for comment.

A security note for the site warns that in case of a major fire, products present there were likely to result in the emission of cadmium through fumes.

Cadmium is highly toxic and dangerous to the environment, but the note said that considering the environment of the factory and the behaviour of toxic fumes, these should not pose an immediate health risk to residents.