Police in northern France have launched an official probe into the gas leak at a Rouen factory which that caused a stink as far away as Paris and the UK.

• Pong from French gas leak reaches UK (22 Jan 13)

According to French radio RTL the owners of the Lubrizol factory will be investigated on suspicion of"endangering the lives of others".

On top of the police investigation France’s Ecology Minister Delphine Batho, who has suggested negligence" was the cause of the leak, also announced an official inquiry had been opened to determine the cause of the gas leak and who was responsible.

An operation was also underway on Wednesday to neutralize gas leaking from the plant.

The process to deal with the leaking Mercaptan gas began at 5am local time and is expected to last a number of nights.

The operation will aim to transfer the gas from the leaking container into a different one which contains a sodium solution.

“The first step for us is to make sure all necessary precautions are taken,” a spokesman for the management said. “It’s better that we take our time than we take risks.”

A cordon was still in place around the plant on Wednesday morning with traffic still restricted in the nearby area.

Anglo press delight in 'French stench'

On Tuesday the stench of rotten eggs wafted across Paris and northern France, even reaching across the sea to England. The French press noted how their British counterparts seized the opportunity to engage in their favourite past-time of French bashing. Headlines such as 'Le Pong', 'Poo la la' and 'French stench invades England' could be read online by Tuesday afternoon.

"The gas leak has once again given the British press an opportunity to wind up the French," lamented France's La Tribune newspaper.

Headaches, sore throats and nausea were nevertheless among the complaints listed in calls made overnight to emergency lines in Paris by more than 10,000 people worried by the stink that had invaded their streets and homes.

Authorities insisted, however, the gas was harmless.

The leak began early on Monday at a plant run by Lubrizol, a firm that is part of billionaire US investor Warren Buffett's empire, and within a day its odour had reached millions of people across northern France.

Winds carried the invisible gas around 100 kilometres (60 miles) down the densely populated Seine river valley to Paris, and later northwards over the Channel and into England, where it even reached as far as south London.

Mercaptan is normally added to municipal gas, because its sulphurous smell alerts people to gas leaks.