The US has called off the official search for the UFOs shot down over North American with an official saying they may never be found.
Three flying objects were shot out the sky by the US military last weekend.
White House spokesman John Kirby said they may be "tied to commercial or research entities and therefore benign" but he also said it would be difficult to find the motive or origin behind the three, unless they were recovered.
Concerns over unidentified balloons have been heightened after a Chinese balloon the US said was being used for spying was shot down off South Carolina earlier this month.
The Chinese government has said it was a weather balloon.
US officials have now called off the search for the two unidentified balloons that came down in remote areas of Alaska and Lake Huron saying conditions made it too difficult to continue the search.
Canadian officials are continuing to look for the third in the Yukon.
Mr Kirby, a spokesman for the National Security Council, gave his latest update on Friday, saying: “It’s very difficult until you can get your hands on something to be able to tell, and because of where it is over Lake Huron, we all have to accept the possibility we may not be able to recover it.”
Hitting back at criticism of Biden's decision to shoot the balloons downs, Kirby said: “Given the situation we were in, the information available, the recommendation of military commanders, it was exactly the right thing to do at exactly the right time."
He added: “You make decisions based on the best information that you have.
“And ultimately you have to come down to some core principles when you’re making decisions as commander in chief.”
The news comes after Chairman of the Joint Chiefs of Staff Mark Milley revealed the most recent strike over Lake Huron missed its target.
A "small, metallic balloon" was spotted floating over Lake Huron in Michigan, US, on Monday, which President Biden ordered to be shot down.
However, the military missed in its first attempt and had to deploy a second Sidewinder, which hit the target, but it is unsure where the first missile landed over Lake Huron.
It was revealed the US spent nearly $1million (£822,000) on two missile attempts.
Wang Wenbin, a spokesman for China's Ministry of Foreign Affairs, hit out at America's response to spending nearly $1million on firing a balloon.
He said: "Many in the US have been asking, 'what good can such costly action possibly bring to the US and its taxpayers?'"
