It follows a damning report into the Tawel Fan ward at Glan Clwyd Hospital.
Simon Dean, interim chief executive of Betsi Cadwaladr health board, confirmed nine staff have been reported to the Nursing and Midwifery Council and three to the General Medical Council.
He will give an update on action being taken at a meeting on 11 August.
Nine members of staff have been suspended, another four redeployed and three placed on restricted duties.
The number of staff reported to their professional bodies over care at a Denbighshire mental health ward has risen to 12.