FORT COLLINS, Colo. — A homemade balloon aircraft floated away from a yard in Colorado after a 6-year-old boy was seen climbing inside, setting off a frantic scramble by the military and law enforcement agencies before the balloon slowly touched down in a field.

The child's fate was unclear, and there was no sign of him in the balloon when it landed. Authorities feverishly searched for any sign of the child on the ground, including in the neighborhood where he lives.

The bizarre scene played out live on television as the balloon rotated slowly in the wind, tipping precariously at times before gliding to the ground.

Cathy Davis of the Larimer County Sheriff's Department told reporters the balloon was owned by the boy's parents and tethered behind the family's home. She said two sons were playing outside when the older boy saw the younger one go into a compartment at the bottom of the balloon and fly away.

"We'll just have to respond the best we can," Davis said. "This is a first and we'll do what we need to do."

She said the family was in contact with experts to provide details on the craft, including what it's made of and what might happen when it reaches the ground.

The Colorado Army National Guard sent an OH-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.