A foul-smelling cloud of gas which wafted over to parts of the South East from a chemical factory in France has prompted dozens of calls to emergency services.
An accidental discharge of the gas mercaptan from a factory in the northern city of Rouen travelled across the English Channel early this morning.
People in Kent, Sussex, Surrey and parts of London reported the unpleasant aroma but emergency services said the gas is harmless and presents no danger to the public.
Sussex Police said they had received more than 25 calls by 9.15am, neighbouring Surrey had 15 calls by 11.30am, and Kent Police reportedly had a large number of calls.
"We understand that this smell emanates from an accidental factory discharge in Rouen, more than 60 miles west of Paris," a Sussex Police spokesman said.
"The smell is from an additive to the gas which has an unpleasant aroma but is not toxic and there is no danger to the public."
Mercaptan is added to municipal gas to alert people to gas leaks, among other uses.
According to the French interior ministry, the factory at the centre of the leak is owned by Lubrizol, a subsidiary of investor Warren Buffet's Berkshire Hathaway group.
Kent Fire and Rescue Service said: "South Kent residents are being asked to keep doors and windows closed due to a gas cloud that is believed to have come across from France, following reports of a gas leak from a factory 75 miles west of Paris.
"Kent Fire and Rescue Service is aware and liaising with partner agencies."
The Metropolitan Police tweeted: "We are aware of reports of a strong noxious gas-like smell in some south-east London boroughs - no risks to public."
A Hampshire Fire and Rescue Service spokesman said it had received more than 20 calls about the smell, mostly in the Portsmouth area, with reports that it had been noticed as far north as Basingstoke and Andover and as far west as Ringwood.
Group manager Tony Deacon said: "Our control room has dealt with a number of calls reporting the unpleasant gas smell.
"We want to reassure the public that the gas presents no threat to health and is completely harmless.
Pierre-Jean Payrouse, director of internal operations at Lubrizol France, told BFM television: "It smells unpleasant because it's a gas we use to give an odour to natural gas.
"The problem should be resolved during the day."
A local news website said the gas had caused migraines, irritations and nausea among some residents of Rouen.