"We have no proof of life or death of Michel Germaneau," the French source said.
Earlier on Saturday, a military source in Nouakchott said Mauritanian troops were continuing their raid inside Malian territory against members of an Al-Qaeda affiliated group.
"Combing and tracking operations are continuing against the al-Qaeda terrorist camps and we have been able to seize a new arsenal of weapons, explosives and ammunition," the source said.
The armed group gave France a deadline until next week to arrange a prisoner exchange or it would kill the hostage.
The retired engineer Germaneau, 76, was captured in northern Niger on April 22.