Emmanuel Besnier, scion of the secretive family behind one of the world's biggest dairy groups, is often called "the invisible billionaire", unknown to the French public and even to his own employees.

But an outcry over claims the company hid a salmonella outbreak at a plant making powdered baby milk earned him a summons to the French finance ministry on Friday, a rare test for a CEO who rarely shows his face in public.

Created in 1933 by Besnier's grandfather, Lactalis has become an industry behemoth with annual sales of some 17 billion euros ($20.6 billion), making twarog, or quark, in eastern Europe, kaymak in Serbia and Galbani ricotta and mozzarella in Italy.

With 246 production sites in 47 countries, its list of products stretches as long as a supermarket aisle, including household names like President butter and Societe roquefort.

Two of those brands, Picot and Milumel baby milk, were the subject of chaotic international recalls issued in mid-December after dozens of children fell sick.

A total of 35 children in France have fallen ill from the salmonella contamination, prompting a company spokesman, Michel Nalet, to "apologise once again to parents" on Thursday.

French health authorities said Friday that a child in Spain had also fallen ill after drinking Lactalis baby milk, while another case is being investigated in Greece.

Nalet also said that Lactalis was working "in perfect collaboration" with French officials to contain the outbreak, a claim that was rebuffed by France's increasingly exasperated economy minister, Bruno Le Maire, on Friday.

"If there had been perfect collaboration, I wouldn't have had to sign an order on December 9 demanding the recall of more than 600 shipments of baby milk," Le Maire told French television.

Agriculture minister Stephane Travert told RTL radio that he hoped Besnier would address the contamination publicly after his meeting with finance ministry officials.

"I think that is what our fellow citizens expect," he said.

- 'Nobody ever sees him' -

The fact that Besnier was named head of the group when he was just 29 years old may have reinforced his desire to stay out of the media spotlight.

Now aged 47, even the few media photos of him that exist date from more than 10 years ago.

But anger over the salmonella scandal and claims that Lactalis poorly handled the subsequent recalls may force him to address the mistrust personally.

The scandal deepened this month when French investigative weekly Le Canard Enchaine reported that state inspectors had given a clean bill of health to the Lactalis site in Craon, northwest France, in early September.

They failed to find the salmonella bacteria that had been detected by Lactalis's own tests in August and November, which were not reported to the authorities.

The company said it was not legally bound to report the contamination, and it was only after children started falling sick that inspectors descended on the Craon plant.

It could now face charges of causing involuntary injuries and endangering people's lives.

"Lactalis should understand that transparency is the best security these days, and it should have taken the necessary decisions" sooner, Le Maire said Friday.

But it seems unlikely that Besnier, whose group has paid fines for failing to publish detailed financial data in the past, will change its ways anytime soon.

"His grandfather went to each farm, knew every producer. Him, nobody ever sees him!" said Philippe Jehan, president of the FDSEA agriculture union for the Mayenne region, home of Lactalis's headquarters.

"Personally, in over 20 years of working in the department, I've never once met him."

- Growing mistrust -

Media investigations over the years have uncovered employees who "don't even know what he looks like", while government officials are also hard pressed to secure a meeting with the head of the company that employs 15,000 people.

Stephane Le Foll, agriculture minister in ex-president Francois Hollande's government, said he "never" met with Emmanuel Besnier during his five-year term.

Even when attending matches for the Stade Lavallois football club in the company's hometown of Laval, financed largely by Lactalis, Besnier arrives after the start and leaves before the end -- and watches from behind the darkened glass of a private skybox.

Such secrecy has hardly helped the group's image with the public.

With its dominating market position, Lactalis is regularly accused of driving down wholesale prices for milk to the point where producers can barely cover their costs -- while refusing to budge during bitter negotiations.

Its hardline attitude during the most recent pricing standoff late last year prompted the government to organise talks to break the impasse, which wound up in December.

"Lactalis plays up its use of French milk and its know-how in its advertising, but it pays us the same price for our milk as it pays in India," one farmer from Britany said at the time.