"Smoke from fire on the Perle is not radioactive. There was no nuclear fuel on board. Reminder: France has sensors installed across the country for detecting any radioactivity anomaly. Watch out for fake news," the prefecture said on Twitter.
In a thread of tweets, the prefecture said that local firefighting brigades were pulled to the scene along with support teams from neighbouring Marseilles.
According to the statements, no casualties ensued as a result of the fire.
Perle is one of the six Rubis-class nuclear submarines owned by the French navy, all of them are named after gemstones. It was floated out in 1987 and began operations in 1993. Since January, it has been docked in Toulon for maintenance.