French police were expected to release without charge on Friday the last six of 10 suspected Islamic militants arrested in dawn raids two days earlier, legal sources said.
Four were freed on Thursday after prosecutors found there was insufficient evidence to hold them. The sources would not confirm the exact timing of the release of the remaining six on Friday.
French officials said on Wednesday the suspects had been detained preventatively because they had a "similar profile" to Mohamed Merah, a 23-year-old al Qaeda-inspired gunman who shot dead seven people, including three Jewish schoolchildren, in southwest France last month.
A police source described those held as "isolated individuals who are self-radicalized".
He said the suspects had been tracked on Islamist forums expressing extreme views and had been preparing to travel to areas including Afghanistan, Pakistan and the Sahel belt of West Africa to wage jihad (holy war).
Some of those arrested had already visited these areas, the source said.
President Nicolas Sarkozy, who faces an uphill task to win re-election in a two-round election this month and next, has vowed to root out any form of militancy following Merah's killing spree.
Some of Sarkozy's political rivals suggested the wave of detentions was carried out for electoral ends.
Police arrested 19 people suspected of Islamist militancy last week. Thirteen are still being held, alleged to have links to French radical Islamist group Forsane Alizza (Knights of Pride) and being investigated on suspicion of terrorism.