In a statement, police said Helen Gregory, 79, was found dead in her home at Baroda Street about 11.50pm on 24 January.
Initially police had been treating her death as unexplained, but on Sunday Detective Senior Sergeant Tim Leitch said the post mortem showed "Helen died as a result of a violent act".
"Our thoughts remain with Helen's family and friends at this difficult time."
A scene examination also remains ongoing in the area, and police staff are expected to remain there for another day or two.
On Thursday, one neighbour told RNZ they were surprised they had not heard anything on the quiet street.
"It's pretty scary yeah...
"I was talking to the other neighbours around the back, even closer to us, and they were like 'We were up at that time ... we didn't hear anything, we should be able to hear these things'.
"Because you can hear everything on this street, but just having something like that happen, it's not very - it doesn't feel too good."
They said they believed a woman lived alone in the house at the scene of the investigation.
Another resident told RNZ nothing like this had happened in the area before.
Officers knocked on his door to ask if he had seen or heard any disturbance overnight, he said, but he did not know anything was wrong until he heard the news this morning.
Police are appealing for the public's help with their investigation, and want to hear from anyone who saw or had communication with Helen in the days before she was found dead. This includes any of her friends or contacts who have not yet been in touch with police.
"We also want to hear from anyone that was in Baroda Street on Wednesday 24 January, and who may have seen any unusual activity, or seen anyone they didn't recognise as resident in the area."
Anyone with information can report it to police on 105, or make a report online at 105.police.govt.nz, clicking "Update Report", reference the file number 240125/1641.
