Dozens of worried people across Brighton and Hove have called the police, fire service and council about a foul smelling gas leak.
Cardinal Newman Catholic School in Hove closed early for the day, believing the leak to be on its premises.
And other schools were contacting parents offering the chance to collect their children early.
But the smell is the result of a pungent discharge from a factory operated by the American chemicals company Lubrizol in Rouen in Normandy.
The emergency services were keen to reassure the public that the French stench posed no danger to health.
East Sussex Fire and Rescue Service said: “It is understood that the smell has come from an accidental factory discharge, which has blown over from France.
“The smell is from a substance added to natural gas which has an unpleasant aroma but is not toxic and there is no danger to the public.”
Duty Officer Neal Robinson said: “It appears that a large quantity of mercaptan, the chemical introduced as a stenching agent to natural gas, has been released from a factory in France.”
The gas cloud has prompted complaints across Sussex and Kent.
Mercaptan is a harmless organic compound containing sulphur with a strong unpleasant odour.
Sussex Police had received more than two dozen calls by 9.15am.
And Brighton and Hove City Council emailed schools across the area, saying: “Schools are advised that they can operate as normal.
“Unless you have reason to believe there is a gas leak from within your building, there is no need to contact the National Grid’s 24-hour gas emergency service or emergency services.
“The leak in France is still being worked on. However, the gas should dispel naturally.”