The Colorado State Patrol says the girder is part of one of the on-ramps to C-470 near the Interstate 25 junction.
A Colorado Department of Transportation employee first found evidence of someone possibly living inside the girder and then investigators thought it might be a meth lab.
Traffic was backed up in the area because of all the police activity.
Investigators say they had to put on protective suits before going in.
They discovered it was not a meth lab, but a person was living inside.
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