Yang is a nurse at Waikato Hospital's oncology department.
Waikato DHB interim chief executive Derek Wright said Yang was a long-standing employee.
"Her colleagues are supporting the family and we hope for a safe return."
Detective Sergeant Jason Earl earlier described her disappearance as being "out of character" and said police and her family had serious concerns for her welfare.
Multiple searches were carried out along the Waikato river by the Police National Dive Squad over the weekend and on Monday morning found nothing.
Yang is Korean and was wearing a black puffer jacket, black jeans and round black glasses.
Anyone who may have seen Yang since Thursday evening are urged to contact Hamilton Police on 07 858 6200.