The bizarre flight of a home-made helium balloon, thought to have a 6-year-old boy aboard, was a hoax and publicity stunt, a Colorado sheriff said on Sunday, Reuters reported.

"It has been determined that this is a hoax, that it was a publicity stunt and we believe we have evidence at this point to indicate that this was a publicity stunt in hopes to better market themselves for a reality show," Larimer County Sheriff Jim Alderden told reporters at a press conference.

He said the family faced several charges.

The sight of the flyaway balloon on live television gripped U.S. viewers for more than two hours on Thursday as the silver flying saucer-shaped contraption raced across the Colorado sky, tracked by U.S. National Guard helicopters before the boy, Falcon Heene, was found alive and well in his attic.

Questions were raised after Falcon was asked during an interview on CNN why he had stayed in hiding so long when family members and other searchers were desperately calling his name.

He responded: "You guys (his parents) said that, um, we did this for a show."

Alderden said the parents, Richard and Mayumi Heene, could face charges of conspiracy, contributing to the delinquency of a minor, filing a false report with authorities and with attempting to influence a public servant.

Alderden had previously said the couple would face only misdemeanor charges in the incident.

The Heene family has appeared on the ABC television reality show "Wife Swap" in which families swap mothers to deal with family problems.

Richard Heene has emphatically denied that the incident was a hoax and Alderden initially said that he believed him, largely dismissing skepticism in the media.