The death of a woman on Auckland's Waiheke Island is being treated as suspicious after police were called to her home twice on the day she died.

Detective Senior Sergeant Martin Friend said police believed a select few people had information on the circumstances of the death of Chantelle McLaughlin-Middlemiss on June 2.

He urged those people to come forward and said the 32-year-old's death was suspicious.

Det Snr Sgt Friend said emergency services were called to McLaughlin-Middlemiss’ home on Waiheke Rd, Onetangi twice on the day she died - within an hour of each other.

The first time was at 2.42pm, after it was reported that she might be dead, Det Snr Sgt Friend said.

"These concerns were allayed and no immediate concerns required any intervention."

But an hour later, emergency services were called back.

Det Snr Sgt Friend said people had gone to the home after calls were made to the family.

"At around 3.30pm, people known to the family located Chantelle unresponsive in bed. First aid was provided and emergency services were called," he said.

"Fire and ambulance staff attended but sadly could not revive her, and Chantelle was pronounced deceased."

A police investigation, Operation Gannon, had been under way since June.

"Our investigation is focusing on what took place the hours before emergency services first attended the address finding Chantelle alive and well, to being found unresponsive around an hour later, and those persons Chantelle may have had contact with that day.

"From our investigation we believe that there are some people that have information that is important to the case."

Police were urging those people to come forward.

"I recognise there may be mixed loyalties at play, and some people might feel challenged to come forward," Det Snr Sgt Friend said.

"We are determined on finding out what has led to Chantelle's death. We owe it to her whānau and children to find these answers, so we ask you to speak with us."

He asked anyone with information to contact police on 105 and use the reference number 260602/7353.