PARIS — In France’s cutthroat corporate world, the billionaire Vincent Bolloré has a reputation for being untouchable.
He rules a business empire that includes the global advertising agency Havas, a controlling stake in the media conglomerate Vivendi and rail and port monopolies in Africa. To advance his interests, he has cultivated relationships with presidents and other powerful figures on two continents. And his company has stifled scrutiny of its operations by suing journalists investigating claims of corruption.
That aura of invincibility appeared to be in jeopardy on Wednesday, as judges in Paris placed Mr. Bolloré under formal investigation after the police questioned him for two days over accusations that he helped the presidents of two African nations gain power in exchange for lucrative business contracts.
The inquiry could result in criminal charges against Mr. Bolloré, who is known as the King of Africa for the vast business dealings that have won him untold riches in former French colonies.
A Havas executive, Jean-Philippe Dorent, and a top Bolloré Group official, Gilles Alix, have also been questioned by the police, who searched the Bolloré Group headquarters outside Paris this month.
Investigators from France’s financial crimes unit are examining whether a subsidiary of Havas, whose clients include luxury brands like Calvin Klein and Valentino, facilitated the elections of the presidents of Guinea and Togo and underbilled them for advertising work during their campaigns. Prosecutors are investigating whether the deals paved the way for Bolloré Group, a holding company that manages Mr. Bolloré’s sweeping infrastructure interests, to run container ports in the two countries.
In a statement, the Bolloré Group acknowledged the formal investigation and said that Mr. Bolloré “continues to be presumed innocent” and would “now have access to this dossier (of evidence) whose content he had no knowledge of and will have the opportunity to answer these unfounded accusations.” In a statement on Tuesday, the company had denied all wrongdoing and had said it was cooperating with the inquiry.
Last week, Mr. Bolloré unexpectedly appointed his son, Yannick, to serve in his place as chairman of the Vivendi board. The younger Mr. Bolloré also leads Havas.
Mr. Bolloré’s prolonged detention is unusual in France, where top executives rarely face legal scrutiny. Former executives of Lafarge, the world’s largest cement company, were recently charged with financing terrorist groups in Syria, but it is unclear whether the case will result in convictions. The billionaire French industrialist Serge Dassault paid a fine and avoided jail after going on trial last year for stashing millions of euros in tax havens.
The case has renewed attention on the cronyism that persists between members of the French elite and African leaders and on both parties’ mercantile ambitions in Francophone Africa.
The case is unfolding as Nicolas Sarkozy, the former president of France and a close friend of Mr. Bolloré’s, is being investigated on suspicion of accepting millions of euros in illegal campaign financing from the Libyan dictator Muammar Gaddafi. Mr. Bolloré was previously accused of helping to facilitate the financing, but was not charged.
One of the matters involving Mr. Bolloré now under scrutiny is connected to Alpha Condé, a Guinean politician who is believed to have befriended Mr. Bolloré while he lived in political exile in Paris in the mid-2000s.
After Mr. Condé returned to Guinea to seek the presidency in 2010, an international Havas unit helped guide his campaign, and then allegedly underbilled him for its services. After Mr. Condé won, the Guinea government transferred an agreement to run the container-port terminal at Conakry, Guinea’s capital, to the Bolloré Group from a French rival.
The deal, first reported by the French newspaper Le Monde, added a strategic jewel to the Bolloré Group’s network of assets in West Africa, where it has a virtual stranglehold on much of the transporting of billions of euros worth of cargo. A map of the group’s holdings shows a web of Bolloré-run roads, railways, waterways, airports and ports that covers two-thirds of the continent and employs more than 25,000 people.
A similar pattern emerged in Togo, another former French colony. There, the same Havas unit was said to support, with below-market-rate services, the re-election of President Faure Gnassingbé in 2010.
A few months before Mr. Gnassingbé, who has close ties to Mr. Bolloré, won a second term, his government awarded a contract for the container port at Lomé, the country’s capital, to the Bolloré Group.
In its statement on Tuesday, the Bolloré Group said it had originally gotten a contract to operate the port in 2001, long before Havas was doing business in Guinea. In 2013, Havas stopped doing political consulting for French and African figures after some of its clients, including the former International Monetary Fund director Dominique Strauss-Kahn, became ensnared in scandals.
The Bolloré Group has routinely sued French and African media outlets for defamation over reports on its business dealings on the continent. Journalists at Canal+, a French television channel owned by Vivendi, have accused Mr. Bolloré of using his influence to try to suppress an investigative report about a popular revolt against Mr. Gnassingbé in Togo. Two producers were fired after the report aired in December.
The suits have challenged the media outlets France Inter, France 2, Rue89 and Mediapart, among others. Those reports included investigative pieces alleging that workers at the company’s Socapalm and Safacam units, which operate palm oil plantations in Cameroon, were being exploited.
Since 2009, the Bolloré Group has brought more than 20 defamation suits involving over 40 reporters and nongovernmental organization activists in France, according to Sherpa, a French anticorruption organization that pursues humanitarian abuses by corporations. “Because of their systemic nature, we regard these legal actions as ‘gag suits,’” Sherpa said in a statement.
The Bolloré Group has said the suits were meant to combat what it described as biased reporting.
The judges will now decide whether Mr. Dorent and Mr. Alix should also be placed under formal investigation in France, the next step toward a possible trial. The case could still be dropped if the evidence is found lacking.