A patient has died at Middlemore Hospital after leaving the emergency department because of long wait times.
Counties Manukau District Health Board says it's urgently investigating.
The hospital said the patient left the ED early on Wednesday morning, only to return a few hours later after a life threatening emergency.
The patient died in intensive care.
The DHB said the hospital was under extreme pressure and patient presentations had been abnormally high for this time of year.
Nurses Organisation president Anne Daniels said she was heartbroken when she heard the news.
She said emergency doctors and nurses had been warning for months that unsafe staffing levels would lead to deaths.
Daniels said something must be done to address the situation, or more people will die.