French President Francois Hollande says gunmen who kidnapped a French family of seven in Cameroon this week have probably separated the family into two groups.
Hollande did not specify on Thursday why he believes abductors have split up the family.
He told reporters that French authorities are fully cooperating with Cameroonian and Nigerian investigators to try to locate them and that it was best to work "discreetly."
On Tuesday, unidentified gunmen on motorbikes abducted the family members as they vacationed in a town in northern Cameroon, near the Nigerian border. Four of the captives are children.
Investigators believe the gunmen took the family across the border into Nigeria.
No group has claimed responsibility, but French Defense Minister Jean-Yves Le Drian blamed Nigerian militant group Boko Haram.
The incident prompted France to urge its citizens to leave northern Cameroon.
The French Foreign Ministry said about 6,200 French citizens are registered as living in Cameroon. It is not clear how many are in the northern region.
The ministry warned that France's involvement in the Mali conflict has given rise to explicit threats against French interests and expatriates.