Uniformed officers and a forensics team, including a police photographer, are at a flat on Bledisloe Street and were seen going in and out of the front door in masks and overalls.
A large tent has been set up in the front garden and detectives can be seen dusting the front door frame for fingerprints.
A neighbour said an older woman lived alone at the flat. She often rode a scooter but hadn't been seen for several days.
He said he and another neighbour at the flats had been "tight" with the woman and he was upset she had been "left like that".
The incident was unfolding as many children were leaving nearby Waiopehu College and Levin East Primary School at the end of the school day, with groups walking past the scene.
A team of about five forensic officers are working inside the house while several uniformed police officers are also at the scene.
It is understood police have been working at the property for several hours.
Police have been approached for further information.
