NIAMEY, Niger (AP) — A fire fueled by high winds swept through an elementary school in Niger's capital, killing 20 children, hospital officials said Wednesday.

The pupils — between the ages of 7 and 13 — were attending class at the time the blaze erupted around 4:30 p.m. on Tuesday.

The cause of the fire was under investigation and it was not immediately known where it started. Some of the school's classrooms were inside buildings, though other classes were held outdoors in straw huts.

Prime Minister Ouhoumoudou Mahamadou and Interior Minister Alkache Alhada visited the scene and gave their condolences to the grieving families.