Ex-French President Nicolas Sarkozy has been placed under formal investigation over alleged influence peddling.
He appeared before a judge in Paris late on Tuesday after 15 hours of questioning by anti-corruption police.
This is thought to be the first time a former French head of state has been held in police custody.
Mr Sarkozy's lawyer, Thierry Herzog, and senior prosecutor Gilbert Azibert were also placed under formal investigation over the allegations.
There was no word on the questioning of a second prosecutor, Patrick Sassoust, who had also been in custody.
Mr Sarkozy, who is due to be interviewed live on French TV on Wednesday evening, received support from several high-ranking party colleagues. Former PM Alain Juppe wrote on his twitter feed: "I'm thinking in friendship of Nicolas Sarkozy: he's of course presumed innocent."
Socialist President Francois Hollande also stressed the presumption of innocence, his spokesman said.
When a suspect is placed under formal investigation, he or she is then examined by a judge, who determines whether there is sufficient evidence for the suspect to be charged.
The step often, but not always, leads to trial. Influence-peddling can be punished by up to 10 years in prison and a fine of 150,000 euros (£120,000; $205,000).
Allies of Mr Sarkozy suggested on Wednesday that one of the two judges on the case, Claire Thepaut, was openly hostile to the ex-president. But Prime Minister Manuel Valls stressed the allegations against Mr Sarkozy were serious and the investigation was being carried out independently of the government.