The Iranian government has been holding a second French researcher in custody for the past four months, according to his colleagues.
Roland Marchal, a sub-Saharan Africa specialist at Paris university Sciences Po, was arrested in June when he traveled to Iran to visit his partner, Fariba Adelkhah, according to Sciences Po professor Richard Banegas.
Iranian authorities disclosed in July that they had arrested Adelkhah, a prominent anthropologist who holds dual French-Iranian nationality, on charges that have not been made public.
There was no immediate acknowledgement of Marchal's arrest in Iranian state media.
It's unclear exactly what charges Marchal faces, but Banegas told The Associated Press that he and his colleagues consider him ``an academic prisoner.''
The French Foreign Ministry did not immediately respond to requests for comment.