“I'm not able to categorize how they stay aloft. It could be a gaseous type of balloon inside a structure or it could be some type of a propulsion system. But clearly, they're -- they're able to stay aloft,” he added. 

VanHerck stressed that officials do not know the country of origin of the objects downed in recent days, distinguishing it from the suspected Chinese surveillance balloon that the US military shot down off the coast of South Carolina last week.

“I would be hesitant and urge you not to attribute it to any specific country. We don't know,” VanHerck said.