According to social media accounts, the load was a pressure washer, filled with water. No one was hurt.
The Mercian building is a 42-storey block of flats being built on Broad Street in the centre of Birmingham for developer Moda Living/Apache Capital.
Main contractor for the £183m project is John Sisk & Son. Morrisroe is delivering the substructure and superstructure under subcontract.
A spokesman for John Sisk & Son said that the company was aware of an incident on the, adding: “An investigation was launched immediately to establish the facts and all appropriate measures will be taken on foot of that investigation on this site and all our sites.”
Subcontractor Morrisroe said: “We are able to confirm that no one was injured and we are cooperating fully with the joint investigation with our client Sisk so that we can fully understand the detail.
“We are not currently in a position to provide any further comment on the matter until that investigation has been completed.”