A male youth has been arrested and charged with the murder of Ashburton mother Sina Solomona.
"It came really unexpectedly," Detective Senior Sergeant John Rae said.
The youth appeared at the Christchurch Youth Court this morning.
Police had searched several properties locally.
Rae said it was "certainly" good to have an arrest and it had given investigators a clear definition of where they were going in the investigation, which was still continuing.
The house where Solomona was murdered would be handed back to the family today.
Police inquiries were continuing at a number of sites of interest, Rae said.
"We are continuing to gather evidence to put together a full picture of the events around Ms Solomona's death.''
Solomona's body was released to her family yesterday.
Text messages sent by Solomona showed she was happy and chatty in the minutes leading up to the killing.
Rae said her text messages had given police a clearer idea of when the attack was carried out.
He said the text messages were mainly sent after Solomona left a friend's house, where she had been socialising after finishing work at 1am. She was dropped home by her twin sister's partner about 2am.
Rae said the text messages were "chatty".
"She was happy and normal, just tired after work," he said. "We can account for her right up to the time she got to the house."
Rae did not say what time the last message was sent.
She never sent a distress signal, he said.
Meanwhile, police are waiting on forensic testing to determine if a bloodied handprint found on a clothing bin only a few streets away from the house was left by Solomona's killer.
Police seized all the clothing from the bin and have checked other clothing bins in Ashburton for any items of interest or bloodied clothing.
Rae said forensic testing of the handprint would be "secondary" to testing items from the crime scene.
Investigators spent most of yesterday taking a record of every item that was in the Cass St house.
Rae said Solomona's mother would be taken through the house to see whether anything was missing or if something was there that should not have been.
Investigators believe the killing was planned, and most likely carried out by someone she knew. It was likely the killer knew Solomona would be there by herself and went in the unlocked back door.
Police are considering a sexual element to the attack but there was no evidence of rape.
There was also no evidence of a fight or scuffle, and there was no sign of any defensive wounds to Solomona's hands and arms.
Her stepbrother found her near death in a pool of blood about 2.40am. He ran for help, but she could not be revived.
A weapon was found close to her body, but Rae is refusing to say what it was, or if it was used in the attack.