The building site's top floor was a mess of spilled concrete, tangled wire mesh and bent ceiling props.

Seven people have been injured after a building site roof collapsed in Albany, on Auckland's North Shore.

Police, fire trucks and ambulances were called to the construction site on Corinthian Drive, Albany, just before 6am on Wednesday.

A St John Ambulance spokeswoman said four male patients had been taken to North Shore Hospital with moderate injuries.

CHRIS SKELTON/STUFF WorkSafe staff (yellow jackets) had arrived on site before 8am

Three more patients had been assessed by ambulance staff at the scene but had not needed hospital treatment.

She said it was believed the injured people had fallen about 2.5 metres in the collapse, but no one had been trapped in the incident.

A tangle of metal wire mesh could be seen at the back of the building, bent from the roof to the floor of the second storey.

SIMON MAUDE/STUFF The manager of the building site declined to comment.

A construction industry expert, who did not wished to be named, said it appeared from photographs of the scene that metal mesh, or formwork, had collapsed when concrete was poured.

The manager of the building site declined to comment.

WorkSafe were notified and were on site investigating by 7.40am.