(CNN) — US intelligence officials believe that the recently recovered Chinese spy balloon is part of an extensive surveillance program run by the Chinese military, according to multiple American officials familiar with the intelligence.

The surveillance program, which includes a number of similar balloons, is in part run out of the small Chinese province of Hainan, officials tell CNN. The US does not know the precise size of the fleet of Chinese surveillance balloons, but sources tell CNN that the program has conducted at least two dozen missions over at least five continents in recent years.

Roughly half a dozen of those flights have been within US airspace — although not necessarily over US territory, according to one official familiar with the intelligence.

And not all of the balloons sighted around the globe have been exactly the same model as the one shot down off the coast of South Carolina on Saturday, that official and another source familiar with the intelligence said. Rather, there are multiple “variations,” these people said.

The link to the broader surveillance program, which was uncovered before the latest balloon was spotted last week, was first reported by the Washington Post.

CNN has asked the Chinese Embassy in Washington for comment on the suggestion that the balloon that was shot down is part of a wider surveillance program.

Meanwhile at a government lab in Quantico, Virginia, an elite team of FBI engineers is poring over the remnants of the recovered balloon, trying to learn everything it can about the intelligence it may have gathered and how best to track surveillance balloons in the future.

Sources familiar with the effort say that officials want to understand as much as possible about the balloon’s technical capabilities including what kind of data it could intercept and gather, what satellites it was linked to and whether it has any vulnerabilities that the US might be able to exploit.

And perhaps critically, the investigators will be looking at what digital signatures it emitted to see if they provide a better way for the US to track this kind of balloon in the future. The commander of US Northern Command, Gen. Glen VanHerck, acknowledged to reporters on Monday that the US had a “domain awareness gap” that had allowed past balloons to cross into US airspace undetected.

One source familiar with the FBI operation said the analysis and reconstruction of the balloon’s payload will ideally determine whether the airship was equipped with the ability to transmit data it collected in real-time to the Chinese military or whether the device contained “stored collection” that China would later analyze after the device was eventually recovered.

China maintains the vessel downed by the US was a weather balloon thrown off course but did offer a rare expression of “regret” over it in a statement Friday.

Beijing’s rhetoric hardened significantly after the US military shot down the balloon, with China’s Foreign Ministry accusing the US of “overreacting” and “seriously violating international practice.” The Defense Ministry, meanwhile, expressed “solemn protest,” warning China “reserves the right to use necessary means to deal with similar situations.”

Valuable intel gained from balloon’s transit over US

Defense officials say that the US gleaned important clues to the answers of some of these questions while the balloon was transiting the United States.

The US — using some technical capabilities provided by National Security Agency among other agencies — has already gathered some real-time information on what kinds of signals the balloon was emitting as it traveled, according to one defense official.

“I think you’ll see in the future that that timeframe was well worth its value to collect over,” VanHerck said.

But officials want to be able to examine the balloon’s hardware in order to learn more about its precise capabilities.

“When the balloon is in our hands, we can look at the technology, we can rebuild the supply chain, find out who helped build it, what components were important to it,” said Rep. Jim Himes of Connecticut, the top Democrat on the House Intelligence Committee. “Obviously you can tell its functions and specifications. There’s a very high intelligence value in having it.”

The US will also be trying to find out more about China’s intelligence-gathering priorities in the United States.

But how much the intelligence community will be able to learn about what information the balloon actually collected, or was trying to collect, isn’t clear at this point, several officials said, and will likely depend on how damaged the balloon’s substructure was by the initial shoot down and the 60,000-foot drop into the ocean.

The biggest unanswered question, officials say, remains China’s intent. China continues to argue that the vessel was a weather balloon that drifted off-course and that its path over the United States was an accident. Officials have acknowledged that this type of balloon has only limited steering capabilities and largely rode the jet stream.

But multiple defense officials and other sources briefed on the intelligence say the Chinese explanation isn’t credible and have described the balloon’s path as intentional.

The source familiar with the FBI operation also noted the intelligence community will be interested in learning whether the equipment on the Chinese balloon bears any technical resemblance to technology constructed by the US intelligence community and military, as the Chinese government has long been aggressive in stealing American defense secrets.

Elite team analyzing the wreckage

A specialized team from the FBI’s Operational Technology Division is analyzing pieces of the wreckage, this person told CNN.

This elite team consists of agents, analysts, engineers and scientists, who are responsible for both creating technical surveillance measures and analyzing those of the US’ adversaries.

OTD personnel, for example, construct surveillance devices used by FBI and intelligence community personnel targeting national security threats — but they also are responsible for managing court-authorized data collection and work to defeat efforts by foreign intelligence agencies to penetrate the US.

The full analysis of the wreckage will take an undetermined period of time, the source said, as recovery efforts are still underway.

Meanwhile, defense officials insist that the US learned more about the balloon’s capabilities by allowing it to pass over the United States than they would have by shooting it down immediately — a decision that some lawmakers on Capitol Hill have criticized as a counterintelligence threat.

But, according to one member of the House Intelligence Committee, “there’s number of reasons why we wouldn’t do that. We want to collect off it, you want to see where it’s going and what it’s doing.

“We’re not without defenses,” this person added. “After all, this is a balloon. It’s not a stealth bomber.”

A defense official said the US has procedures — akin to a kind of digital blackout — to protect sensitive locations from overhead surveillance, typically used for satellite overflight.