Police are to file criminal charges against family members involved in Colorado's runaway balloon saga, law enforcement sources confirmed.

Larimer County Sheriff Jim Alderden told reporters on Saturday that officers were preparing search warrants and drawing up charges against eccentric amateur scientist Richard Heene and unidentified members of his family.

Alderden did not specify what charges were likely to be issued against Heene, who underwent a day of further questioning by police on Saturday amid suspicions that the event could have been a hoax.

"We're in the process of drafting search warrants and we do anticipate at some point in the future there will be some criminal charges filed with regards to this incident," said Alderden.

"What those charges will be are most likely misdemeanors, which hardly seems serious enough given the circumstances."

However, the sheriff also said he would be talking with the Federal Aviation Administration and other federal agencies about possible federal charges stemming from the incident.

Police were initially convinced Heene and his family were telling the truth about the circumstances of Thursday's drama, when Heene's six-year-old son, Falcon, was thought to have floated away in a home-made balloon.

The story dominated cable television broadcasts for several hours as millions tuned in to watch the drama unfold.

More than 80 law enforcement officers, news helicopters and search crews tracked the balloon Thursday as it soared 762 metres above the ground for more than 80.5 kilometres before landing in a field near Denver International Airport.

The balloon was empty, prompting concerns the boy had fallen from it. Several hours later, Falcon came down from an attic space where he had been hiding as the search escalated, sparking joyous scenes.

Saturday's latest developments came at the end of another bizarre day which had begun with Heene telling reporters camped outside his Fort Collins home to stand by for a "big announcement."

He finally emerged from his house carrying a cardboard box which he asked reporters to put written questions into for his consideration.

He brushed off shouted questions apart from one which asked him to confirm "once and for all" if the balloon drama had been a hoax.

"Absolutely no hoax, I want your questions in a box and I'll get right back to you, okay?" Heene said.

Skepticism about the saga was fueled late on Thursday when Falcon Heene said during a CNN interview that he had not come out of his hiding place during the drama because "you guys said that we did this for the show."

However in an emphatic show of support for the Heene family on Friday, Alderden said he was certain that officers had not been duped, citing the parents anguished state when Falcon was missing.

Meanwhile patience among the Heene family's neighbours was wearing thin on Saturday, the Denver Post reported as the circus continued.

"C'mon, Richard, get this over with," said one 32-year-old neighbour who asked not to be identified. "Let the neighbourhood get back to normal. We're sick of it."

Local residents and brothers Paul and Jarrod Pocarnsky carried signs laced with irony. Paul Pocarnsky's banner read: "10-15-09 We will never forget."

"This is big," Pocarnsky said. "This is a memory for life."

Brother Jarrod meanwhile held a sign that read: "Put balloon boy on TV: America's Most Wanted."

AFP

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