France has launched an investigation into suspected kickbacks over deals worth $2.5 billion reached by the French and Kazakh governments when Nicolas Sarkozy was president.
The "Le Monde" newspaper reported on October 7 that a formal investigation of suspected money laundering was opened in March last year.
This was confirmed to the Associated Press news agency by a Paris judge, who spoke on condition of anonymity because he was not authorized to speak publicly about the matter.
Preliminary charges of corruption and money laundering were filed last month against three people, including a lawyer for one of Sarkozy's aides at the time, the judge said.
Several deals, including the sale of 45 helicopters by French group Eurocopter, were signed during a Paris visit by Kazakh President Nursultan Nazarbaev in October 2010.
Based on reporting by lemonde.fr and AP