By Keith Coffman
DENVER (Reuters) - Rescuers hunted Thursday for a 6-year-old boy believed to have climbed into a homemade helium balloon before the craft took off and drifted across Colorado, saying that he may have been in a basket or box that fell off the contraption.
The silver craft, shaped like a flying-saucer, was shown live on television for hours across the United States as it soared up to 7,000 feet (2,100 metres) and drifted for miles across the Colorado skies, landing gently in a field after slowly deflating.
Rescue crews rushed to the collapsed balloon, which was built by the boy's amateur scientist father and had been tethered to the ground at the family's back yard in Fort Collins, but found no sign of the boy.
Authorities focussed their search on a small basket or box that they believe had been attached to the bottom of the small helium airship, but said they were still not certain that 6-year-old Falcon Heene was ever inside.
"There is an active ground and air search under way but it's possible that the boy was not in the basket that was attached to the craft," Colorado Division of Emergency Management spokesman Kevin Kuretich told Reuters.
CNN reported that witnesses told police they saw an object fall from the balloon as it sailed over Platville, Colorado, and that rescue crews were concentrating on the area as well as the balloon's flight path.
The network broadcast a still picture of the balloon with a dark object below it that could be an object that had fallen from it.
Larimer County Sheriff's deputies also conducted an exhaustive search of the family's neighbourhood.
The bizarre scene played out live on cable TV networks as the balloon drifted for some two hours across Colorado, chased by helicopters as authorities tried to figure out how to safely bring it down.
The boy's father, Richard Heene, was described as a storm chaser and amateur scientist who had involved his entire family in his activities.
The family also participated in the ABC-TV reality show "Wife Swap," in which families switch mothers to deal with family problems.
On its website, ABC described the Heene family as devoting their time to "scientific experiments that include looking for extraterrestrials and building a research-gathering flying saucer to send into the eye of the storm."
Aviation experts said the boy could have survived the flight, but questioned whether such a small craft could have supported the weight of the boy and compartment for long.
(Writing by Dan Whitcomb, Editing by Sandra Maler)