A man who later tested positive for Covid-19 evaded security at North Shore Hospital to visit another person there.
A number of people have been stood down at the hospital as a result to be tested.
The man acted evasively to breach the hospital's Covid-19 rules on 16 September.
"He bypassed our front-of-house screening processes while staff were assisting another person and hid from security staff before running into a lift," Waitematā District Health Board executive director Mark Shepherd said in a statement.
"He briefly visited Ward 7 and our Assessment and Diagnostic Unit before he was confronted by security and escorted from the building. He was on-site for just under 30 minutes in total."
The man tested positive for Covid-19 yesterday, according to the DHB.
"This person has acted deceptively to break the rules everyone else has followed and potentially exposed people to the virus in the process."
The hospital is working with police.
Look back at today's developments here: