Abdou Labo said a resident was standing just a few meters from where the body landed at around 5 a.m. Thursday. He said police arrived and found "the lifeless body of a black person, lying in blood."
He also said blood had been spotted on the left wing of the plane.
Labo said the plane was coming from Burkina Faso's capital, Ouagadougou, and was scheduled to continue to Paris.
Officials were holding the plane in Niamey so crew members and passengers could be interviewed. Investigators in Ouagadougou are also looking into "the conditions in which the passengers boarded."