Who invented n-categories?

Can anyone offer a reference to the first published work which defined a notion of strict n-category equivalent to that used today? I know that Ehresmann invented n-tuple ( or n-fold ) categories which contain strict n-categories as special cases. If this is the first implicit defintion of strict n-category does anyone know who was the first to isolate our current notion of strict n-category as a particularly interesting special case of an n-tuple category? Carl Futia