"This appears to have been triggered by a very strong gust of wind dislodging a clip on the plank. The scaffolding system has been installed as per the manufacturers specification and an investigation is underway to confirm the root causes.
"The plank did not go through the roof but did cause damage to the surface membrane and ceiling, leading to some water ingress in the corridor beneath."
A SkyCity spokesman said the metal plank damaged two windows and a roof, causing it to leak.
"I can confirm that as a result of a piece of scaffolding falling from Auckland Council's building, there was some damage to two windows and the roof of the SkyCity Grand Hotel.
"This resulted in some minor water damage to the Grand Hotel gym area. Fortunately no one was injured."
Mr Ramsay said the council's contractor and the scaffolding subcontractor were working with SkyCity to repair the damage, which will be covered by the contractor's insurance.
He said the scaffolding system was thoroughly checked and additional safety measures put in place.
A WorkSafe spokesman said the agency was notified of the incident and was still deciding if any action would be taken.