PARIS (Reuters) - Eight suspects have been placed under formal investigation in France following their arrest in joint counter-terrorism raids with Swiss authorities, a judicial source said on Saturday.

The suspects were among 10 detained on Nov. 7 by French and Swiss police as the result of a four-month investigation into a group of young Islamists thought to have been radicalized by a Swiss imam, who was among those detained. [nL5N1ND33T]

Following the arrests, French Interior Minister Gerard Collomb told French lawmakers the group was believed to have been planning attacks but had not yet chosen specific targets.

Seven of the eight suspects placed under formal investigation have been remanded in custody, the judicial source said. A ninth person arrested in the French swoop was released without charge.