A homemade experimental helium balloon crash landed in a Colorado field but there was no sign of the six-year-old boy thought to have been inside.

At the moment no one knows the whereabouts of the boy, whether the boy really did get into the balloon or whether he did get in but then subsequently fell out.

According to reports from CNN A sibling saw the boy get into the craft Thursday morning.

The balloon made to look like a UFO floated away from the family's Fort Collins home after the boy untied it according to several media reports.

Television images showed the silver balloon floating across the Colorado skies at an estimated 6,000 feet, moving at an estimated 30 miles per hour.

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