Captain Mark Weiss says he's not sure what happened to the flight, but "I think there was a some kind of a struggle in airplane."
More French troops are headed to the West African country of Mali to fight Islamist extremists who have seized a town and its strategic military camp.
Several thousand soldiers from West African nations neighboring Mali are also expected to begin arriving soon. Nigeria said nearly 200 of its troops would arrive in Mali in the next 24 hours.
French President Francois Hollande launched an attack on Mali’s rebels, who are linked to al-Qaida, last week after the insurgents began advancing south.
France’s action preempted a United Nations-approved plan for a military operation in Mali, which was expected to start about nine months from now.
Hollande decided a military response could not wait that long in its former colony.