PARIS — Former President Nicolas Sarkozy of France was questioned by the police on Tuesday as part of an investigation into whether his 2007 election campaign received illegal financial support from the Libyan regime of Col. Muammar el-Qaddafi.
Mr. Sarkozy, 63, was taken into custody in Nanterre, northwest of Paris, after answering a police summons, according to a French judicial official who spoke on the condition of anonymity, in line with department policy.
Under French law, Mr. Sarkozy can be held for up to 48 hours before either being released or formally placed under investigation and charged.
The corruption investigation involving Mr. Sarkozy and his 2007 election campaign was opened in 2013, but Monday was the first time he had been questioned by police in that case. He has repeatedly denied any wrongdoing.
Brice Hortefeux, a close ally of Mr. Sarkozy’s and one of his interior ministers, was also summoned for questioning by the police on Tuesday as part of the investigation.
In France, complex criminal cases are handled by special magistrates with broad investigative powers. Defendants placed under formal investigation do not automatically go to trial: Magistrates can drop cases they believe have insufficient evidence.
The suspicions behind this case first emerged in 2012, when the investigative news website Mediapart published a report suggesting that Mr. Sarkozy’s 2007 campaign had received up to 50 million euros, or nearly $62 million at current exchange rates, from the regime of Colonel Qaddafi, the longtime Libyan strongman who was killed in 2011. Such support would have violated France’s strict campaign finance laws, which cap spending and prohibit foreign funding.
Since those first reports, aides to Mr. Sarkozy and middlemen who knew him and who acted as political and financial intermediaries between France and Libya have come under close scrutiny by the police and the news media.
In 2015, Claude Guéant, a top aide and former interior minister to Mr. Sarkozy, was charged in connection with the investigation.
Ziad Takieddine, a French-Lebanese arms dealer who had introduced Mr. Sarkozy to Colonel Qaddafi, told Mediapart in 2016 that he had personally delivered suitcases with €5 million in cash to Mr. Sarkozy and Mr. Guéant shortly before the 2007 election. Both politicians denied the account by Mr. Takieddine, who has also been charged in the investigation.
In January, Alexandre Djouhri, a French businessman who is close to Mr. Sarkozy and who also acted as a financial intermediary with Libya, was arrested in London in connection with the investigation. The French authorities are seeking his extradition.
Mr. Sarkozy won the 2007 election but failed to secure a second term in 2012. He later went on to head the center-right party Les Républicains and tried to mount a political comeback, but he lost in the party’s primaries for the 2017 presidential elections.
Since the end of his presidency, Mr. Sarkozy has faced multiple corruption inquiries, which are at various stages, and he has always denied any wrongdoing. In some cases, the charges were dropped; in others, investigations are continuing.
In the so-called Bettencourt affair, for instance, in which Mr. Sarkozy was suspected of manipulating the heiress to the L’Oréal fortune into financing his 2007 campaign, the charges against him have been dropped.
But in another case, involving illegal overspending during his bid for re-election in 2012, he has been ordered to stand trial.
In yet other cases, people close to Mr. Sarkozy have been charged and his name has been cited, but he has not been charged himself. Of those cases, the one involving suspicions of Libyan financing is the most complex and, potentially, the most serious for the former president.