The United States, on Friday, concluded its search for debris from an a suspected Chinese surveillance balloon which was shot on February 4.

"Final pieces of debris are being transferred to the Federal Bureau of Investigation Laboratory in Virginia for counterintelligence exploitation," said the US military's Northern Command in a statement.

The search for two of the three other objects shot down near Alaska and on Lake Huron has also ended, said the statement.

The Northern Command said that the air and maritime safety perimeters were being lifted at both sites.

'Significant amount' of debris collected — White House

According to officials, much of the balloon had fallen into about 50 feet of water.

The Navy collected remnants floating on the surface, while divers and unmanned naval vessels pulled up the rest from the ocean floor.

White House national security spokesman John Kirby said that a significant amount of debris, including "electronics and optics," were recovered.

The debris included key equipment which could reveal what the balloon was able to monitor and collect.

Kirby declined to say what the US had discovered from the wreckage thus far but said a lot had already been learnt by observing the balloon as it drifted over the US.

"We're going to learn even more, we believe, by getting a look at the guts inside it and seeing how it worked and what it was capable of," he said.

An official told AP news agency on the condition of anonymity that the US had tracked the balloon for several days after it left China.

President Biden demands 'sharper rules'

With regards to the search conducted near Alaska and on Lake Huron, the Northern Command said that they "did not locate debris."

Earlier this week, President Biden said that according to preliminary evidence, the two incidents were not related to a broader Chinese spy program.

On Thursday President Joe Biden directed national security adviser Jake Sullivan to lead an interagency team to establish "sharper rules" to track, monitor and potentially shoot down unknown objects.

US and China tensions

The announcement to end the search for debris capped three dramatic weeks that saw US fighter jets shoot down four airborne objects — a large Chinese balloon and three smaller objects.

They are the first known peacetime shootdowns of unauthorized objects in US airspace.

China has maintained that the device was for weather surveillance and had gone astray.

Relations between China and Washington have been increasingly tense since.

US Secretary of State Antony Blinken postponed his visit to Beijing earlier this month.

The trip would have been the first by a US secretary of state to China in five years where both sides would have sought to stabilize increasingly fraught ties.

US officials have been looking at the possibility of a meeting between Blinken and China's top diplomat Wang Yi on the sidelines of the Munich Security Conference that began on Friday.