PARIS — French investigators searched Nicolas Sarkozy’s home and office on Tuesday as part of an investigation into suspected illegal financing of the former president’s 2007 presidential campaign by the L’Oreal cosmetics heiress, an official said.

Potential legal troubles have threatened Sarkozy since he lost the presidency to Socialist Francois Hollande in the May elections. Sarkozy, who lost his immunity from prosecution June 15, denies wrongdoing.

Judge Jean-Michel Gentil and other investigators from the Paris financial crimes unit conducted Tuesday’s search of Sarkozy’s home and offices, the official said. The official spoke on condition of anonymity because he was discussing an ongoing investigation.

Messages left with Sarkozy’s staff were not immediately returned.

The probe centers on the finances of France’s richest woman, L’Oreal cosmetics heiress Liliane Bettencourt.

A long-running family feud over her fortune ballooned in 2010 into a multilayered investigation and political affair. Allegations emerged that Bettencourt provided illegal campaign cash to Sarkozy’s party during the 2007 campaign. Sarkozy vigorously denies the claims.

The allegations struck a chord with Sarkozy’s critics, who were frustrated with his handling of the recession-hit economy and saw him as too cozy with the rich.

An accountant for Bettencourt said in 2010 that she gave $62,900 in cash in 2007 to Sarkozy’s party treasurer for the presidential campaign — well beyond the $5,797 legal limit on individual donations.