The hole, which first appeared on August 12, is in the central Place Debouverie, near to the Mairie and just in front of the brasserie La Bonne Humeur.

Municipal police first noticed that the road appeared unstable during a routine morning patrol at 6h40, and quickly alerted the three residents living in the building above the brasserie, who were evacuated.

Water, electricity and gas supplies were cut to the road, and police have now cordoned off the area pending investigation and repair. The area is now said to be stable.

Six businesses, including the brasserie, have been closed as a precaution.

Un trou béant sur le trottoir et la chaussée derrière la mairie d'Amiens. Une canalisation d'eau aurait rompu tôt ce matin. Pas de blessé les agents de GrDF et les pompiers interviennent. Périmètre bouclé pic.twitter.com/wk7PnKoEQ9 — France Bleu Picardie (@fbleupicardie) August 12, 2019

Caroline Merle, risk assessment technician for the town, said: “The earth has now stabilised and there is no [further] risk of collapse.”

Brigitte Fouré, mayor of Amiens, said: “I am happy that no-one was injured. At another time of day - and not bang in the middle of August - we could have had a real catastrophe.”

The exact cause is not yet known, but the town has ruled out the possibility that it could be due to a water leak. Experts have suggested that the hole is due to an underground cavity collapse, according to local newspaper La Voix du Nord.

Others have added that the underground caverns of Amiens - including dozens or even hundreds of cellars dating back to medieval times - could be to blame, according to a report on local news station France 3.

Some of the caverns do not even appear on old blueprints of the town’s underground network, experts said, making the job of tracing and explaining the collapse even more difficult.