France has launched an investigation into suspected kickbacks over deals worth 2 billion euro ($2.5 billion), signed between the French and Kazakh governments when Nicolas Sarkozy was president.

Le Monde newspaper reported Tuesday that a formal investigation on suspicion of money laundering was opened in March 2013. This was confirmed to The Associated Press 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 the lawyer of 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 Nazarbayev in October 2010.