A power generator powering a house is believed to responsible for the hospitalisation of five people with carbon monoxide poisoning in West Auckland overnight.
Fire Service spokesperson Nicole Bernard said crews received a call from St John Ambulance following reports the five people were "sick and vomiting" due to carbon monoxide poisoning at a Jever Place, Massey address at 12.22am.
Two males and three females aged nine to 53 years of age, were found semi-conscious and were taken to North Shore Hospital, one in a critical condition.
Police said emergency services were contacted by a family friend who had been called around to the house after the occupants began feeling unwell, police said.
Fire service investigators and police detectives are at the address this morning to determine the cause of the high levels of carbon monoxide.
Ms Bernard said ambulance staff reported a generator had been running inside with no windows open.
The petrol generator was being used in an attached garage to supply power to the house, police said.