(CNN) — Recovery operations have concluded for the suspected Chinese spy balloon that was shot down off the coast of South Carolina earlier this month, the US military said in a statement Friday.

The recovery effort ended after “U.S. Navy assets assigned to U.S. Northern Command successfully located and retrieved debris” from the balloon, the statement from US Northern Command said.

“Final pieces of debris are being transferred to the Federal Bureau of Investigation Laboratory in Virginia for counterintelligence exploitation, as has occurred with the previous surface and subsurface debris recovered. U.S. Navy and U.S. Coast Guard vessels have departed the area. Air and maritime safety perimeters have been lifted,” the statement added.

US officials are less optimistic about recovering debris from the three objects shot down over North America last weekend.

White House National Security Council coordinator for strategic communications John Kirby said Friday that it’s very possible the US and Canada will not be able to identify all three of the unidentified objects.

“We would like nothing better, but I can’t sit here and promise you that we’ll get to that level of fidelity of detail,” Kirby said at a White House press briefing.

He noted the “extremely bad winter weather” up in the North of Alaska and “arctic conditions” that are making recovery efforts extremely difficult. He also said that the Royal Canadian Mounted Police have been unable to find the object downed in the Yukon territory and that the Canadians have decided not to look for the object that fell into Lake Huron, while the US has still not determined if they’ll be able to mount a search.

“So pretty tough conditions, going to be very difficult to find them, let alone once you find that debris be able to do the forensics to identify it. So I can’t promise you that we’ll know definitively one way or the other,” he added.

US officials have said that the Chinese balloon had a payload — or the equipment it was carrying — the size of roughly three buses and was capable of collecting signals intelligence and taking photos. The balloon traveled over sensitive sites in Montana, officials have said, but the administration has said it tracked the balloon’s path and worked to minimize its intelligence collection capabilities.

The US has said that the balloon is part of a large fleet controlled by the Chinese military that has conducted surveillance over at least 40 countries across five continents in recent years.

CNN reported this week that the US intelligence community is examining the possibility that the balloon, which lifted off from Hainan, China, in January, did not intend to travel over the continental US but was blown off its path by strong winds. The balloon’s original surveillance target was likely Guam, but the weather may have shifted the balloon northward, officials said.

President Joe Biden said Thursday that he expects to speak with Chinese President Xi Jinping about the balloon but that he will not apologize for shooting it down.

“I hope we are going to get to the bottom of this, but I make no apologies for taking down that balloon,” he said.

After the Chinese balloon was shot down, the US military downed three subsequent objects that were much smaller and are now believed to have not been tied to any country’s surveillance program, Biden said. Instead, they were likely used for weather or research purposes by private entities.

The US will be crafting parameters moving forward on how to handle unidentified objects in US airspace that could pose a risk to civilian aircraft, Biden said.

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