The “intestines” of Chinese “spy” balloon shot down in US airspace and at the heart of recent surveillance concerns being analyzed by the US.

The military ended efforts to collect sensors and other debris from the Chinese balloon on Friday as investigators from the Federal Bureau of Investigation (FBI) have begun to investigate its inner workings.

The shooting down of the balloon has sparked a war of words between the US and Chinawhich already share strained ties and have sparked surveillance concerns in the US.

The US military also shot down three unidentified “objects” were found over Canada, Alaska and Lake Huron last weekend, in the aftermath of the balloon incident.

“It’s a significant amount (of recycled material), including the payload structure as well as some of the electronics and optics, and everything that is now at the FBI lab in Quantico,” John Kirby, a spokesman for the National Security Council, said on Friday.

“We’re going to learn even more, we think, by taking a look at the stomach inside it and seeing how it worked and what it was capable of,” he told a White House briefing.

The military said the last pieces of debris recovered from the downed Chinese balloon are being transferred to the FBI laboratory in Virginia for “counterintelligence exploitation.”

In a separate statement the same day, the US Northern Command pointed out that it did not “locate” any debris from two of the three “objects” it had been shot down near Deadhorse, Alaskaand over Lake Huron and said it had called off the search for those items as well.

“The US military, federal authorities and Canadian partners conducted systematic searches of each area using a variety of capabilities, including airborne imagery and sensors, surface sensors and inspections, and underground scans, and found no debris,” the statement said.

“US Northern Command recommended that search operations end today near Deadhorse, Alaska and on Lake Huron, as search activities have not detected any debris from airborne objects shot down on February 10 and February 12, 2023,” it said.

While the US military is convinced that the suspected surveillance balloon shot down off South Carolina was of Chinese origin, the other three smaller objects were probably civilian-owned balloonsReuters reported.

These announcements come after three dramatic weeks in the United States that have raised several questions, including whether and what intelligence the Chinese balloon was able to gather as it flew over sensitive US military sites, and whether it could transmit data back to China.

Earlier on Thursday, US President Joe Biden called on an interagency team to develop “tougher rules” for tracking, monitoring and shooting down unidentified aerial objects in US airspace.

Such unidentified objects have reportedly been spotted in the past over the US Western Pacific Territory Guama strategic hub for the country’s navy and air force.