PARIS, Dec 18 (Reuters) - The former right-hand man of Nicolas Sarkozy was released by French police late on Tuesday after being questioned over his suspected involvement in the alleged misuse of public funds when he served in the interior ministry, a judicial source said.
Claude Gueant, who was the former president's chief of staff when Sarkozy was interior minister and then rose to become interior minister himself, was put under "preliminary investigation" in June.
Police said then they had found evidence of cash purchases worth some 20,000 euros ($27,500) that were unaccounted for in a search of his home. They are now investigating a wider bonus structure in which he received 10,000 euros a month.
Gueant, who was Sarkozy's chief of staff between 2002 and 2011, has denied any wrongdoing and says the 10,000 euro-payments were drawn from a cash fund used to finance police informers and surveillance operations when Sarkozy was interior minister. Sarkozy was elected president in 2007.
Gueant was released shortly before midnight on Tuesday after being questioned most of the day at the headquarters of the judicial police in the Paris suburb of Nanterre.
A preliminary investigation means police can continue to gather evidence with a view to pressing formal charges but it does not automatically lead to an indictment.
Michel Gaudin, another close Sarkozy aide and former head of police, was also released after answering questions about alleged corruption and tax evasion.
The high-profile arrests targeted two former close allies amid media reports that Sarkozy is preparing to run for re-election in 2017.
Sarkozy himself was cleared in October in an investigation into suspicions that he had manipulated France's richest woman into financing his 2007 campaign, removing an obstacle to his return to national politics. ($1 = 0.7271 euros) (Reporting By Nicolas Bertin, editing by Elizabeth Piper)