Wojciech Janowski is still being quizzed over murder of his mother-in-law Hélène Pastor; her daughter Sylvie has been freed without charge.
The son-in-law of wealthy property owner Hélène Pastor is also among those being questioned following her ambush murder in May in Nice.
In a case that has gripped France, Maurice Agnelet, 76, is given 20-year jail term in his third trial for killing of his mistress Agnes Le Roux.
No injuries or significant damage were reported as a result of the quake near Nice which had a magnitude of 5.0.
Maurice Agnelet was acquitted in 1985 of murdering Agnès Le Roux, then freed by European Court of Human Rights after 2007 conviction.
A coffee ordered with the phrase ‘bonjour, un café s’il vous plait’ will only cost €1.40, against €7 for just grunting 'un café' to staff at Nice café.
Interior minister Manuel Valls says justice must take its course after protests over detention of Stephan Turk, who killed a robber outside his shop.
President Hollande drawn into high-profile case which has seen many suporters backing actions of a man who could face life in prison for murder.
A million people on Facebook have backed Nice jeweller who is now under investigation for murder after shooting dead teenager who robbed him.