The men had jumped into a trash bin being lifted by a forklift onto the third floor of an apartment building in Charlotte, North Carolina
when the incident occured.
It is understood that, while in the bin, one of the men had moved shifting the weight and causing the bin to fall off the lift.
The men were taken from the site - which is being developed by the Morgan Group - to hospital with what was reported to be potentially life threatening injuries.
The fall was the second serious incident in the city over recent months.
A worker was injured at another apartment building uptown in October when he fell five stories from the partially built complex.