Three men, aged 26, 27 and 28, and a woman, aged 21, were referred to a court in Paris on Thursday after being arrested earlier in the week near the capital.
The woman and her partner are suspected of setting up a fake loans system to finance sending Islamist youths to fight in Syria.
The group are believed to have organised training in the Paris region and to have been in contact with French "facilitators", who arrange for potential fighters to go to Syria and send them to combat zones.
Investigators think that some of the group had links to the al-Qaeda-linked Islamist Al Nusra Front and want to know more about their relations with a man from Lyon, who is currently in Syria and sometimes referred to as the emir of French fighters there.
He is wanted in connection with several cases, including those of the two school students from Toulouse, south-west France, who were charged in January after returning from the region and of about 10 youths from Strasbourg, of whom at least two have been died in fighting.
In a separate case, two women and a man have been charged in connection with the case of a 15-year-old girl from Avignon stopped at an airport apparently on her way to Syria via Turkey.
One of the women, aged 24, is suspected of putting the teenager up on her way.
She has four children of between one and seven years and is believed to have been preparing to leave to join her husband in Syria.
Security forces in Spain on Friday announced that they had broken up a major Spanish and Moroccan network sending jihadis to Syria.