Completely updated at 5:58 p.m. CDT

IVAN MORENO, P. SOLOMON BANDA, Associated Press Writers

FORT COLLINS, Colo. (AP) — A 6-year-old Colorado boy feared to have floated off in a helium balloon was found safe at his home Thursday, hiding in a cardboard box in the garage attic.

Sheriff Jim Alderman turned to reporters during a news conference and gave a thumbs up and said, "He's at the house." Alderden said an investigator on the scene saw the boy and he was fine, and had apparently been in the attic the whole time.

The giant silvery helium balloon floated away from the family's yard late Thursday morning, sparking a frantic rescue operation after the boy's brother said he saw 6-year-old Falcon Heene get into the balloon.

The flying saucer-like craft, shown live on television nationwide, tipped precariously at times before gliding to the ground in a field, the culmination of a two-hour, 50-mile journey through two counties.

With the child nowhere in sight, investigators searched the balloon's path. Several people reported seeing something fall from the craft while it was in the air, and yellow crime-scene tape was placed around the home.

It was not clear why the boy's brother reported seeing Falcon getting into the balloon.

Kevin Kuretich, of the Colorado Division of Emergency Management, said the craft had some kind of electric power unit which was run by double-C batteries. He said the balloon did seem to be big enough to carry a 6-year-old.

Jason Humbert saw the balloon land. He said he had gotten a call from his mother in Texas who told him about the balloon. He said he was in a field checking on an oil well when he found himself surrounded by police who had been chasing the balloon, which came to a rest 12 miles northeast of Denver International Airport.

"It looked like an alien spaceship you see in those old, old movies. You know, those black-and-white ones. I came down softly. I asked a police officer if the boy was OK and he said there was no one in it," Humbert said.

Neighbor Bob Licko, 65, said he was leaving home when he heard commotion in the backyard of the family. He said he saw two boys on the roof with a camera, commenting about their brother.

"One of the boys yelled to me that his brother was way up in the air," Licko said.

Licko said the boy's mother seemed distraught and that the boy's father was running around the house. The Poudre School District in Fort Collins, where the boys attend, did not have classes for elementary schools Thursday because of a teacher work day.

In a 2007 interview with The Denver Post, Richard Heene described becoming a storm chaser after a tornado ripped off a roof where he was working as a contractor and said he once flew a plane around Hurricane Wilma's perimeter in 2005.

Pursuing bad weather was a family activity with the children coming along as the father sought evidence to prove his theory that rotating storms create their own magnetic fields.

Although Richard said he has no specialized training, they had a computer tracking system in their car and a special motorcycle.

The Heene family appeared twice on the ABC reality show "Wife Swap," most recently in March.

"When the Heene family aren't chasing storms, they devote 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," it says.

While the balloon was airborne, Colorado Army National Guard sent a UH-58 Kiowa helicopter and was preparing to send a Black Hawk UH-60 to try to rescue the boy, possibly by lowering someone to the balloon. They also were working with pilots of ultralight aircraft on the possibility of putting weights on the homemade craft to weigh it down.

But the balloon landed on its own in a dirt field. Sheriff's deputies secured it to keep it in place, even tossing shovelfuls of dirt on one edge.

After the boy wasn't found, a Kiowa helicopter was being equipped with an infrared camera to fly at 1,000 feet and help search the area where something reportedly fell from the balloon, Army National Guard Capt. Michael Odgers said.

The episode led to a brief shutdown of northbound departures from one of the nation's busiest airports, said a controller at the Federal Aviation Administration's radar center in Longmont, Colo.

FAA canceled all northbound takeoffs between 1 p.m. and 1:15 p.m. MDT, said Lyle Burrington, the National Air Traffic Controllers Association representative at the center. The balloon was about 15 miles northwest of the airport at that time.

Before the departure shutdown, controllers had been vectoring planes taking off in that direction away from the balloon, Burrington said.

Federal Aviation Administration spokeswoman Laura Brown said the agency tracked the balloon through reports from pilots.

Neighbor Lisa Eklund described seeing the balloon pass.

"We were sitting eating, out looking where they normally shoot off hot air balloons. My husband said he saw something. It went over our rooftop. Then we saw the big round balloonish thing, it was spinning," she said.

"By the time I saw it, it traveled pretty fast," she said.

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Associated Press writers Dan Elliott, Sandy Shore and Colleen Slevin in Denver contributed to this report.

Copyright 2009 The Associated Press.