An open home was held at a Christchurch property where missing real estate agent Yanfei Bao was either allegedly killed or kidnapped days earlier.
Police visited the house in Trevor St, Hornby on Thursday last week, the day after the 44-year-old disappeared, after learning she had been due to show it to a prospective buyer.
However, they found no obvious sign of anything sinister, and allowed Harcourts to continue to market it –which included an open home on Sunday afternoon.
The property has since become the focus of an intense forensic examination, and the centre of what is now a homicide inquiry.
A 52-year-old man who was arrested at Christchurch Airport on Saturday with no bags and a one-way ticket to Shanghai, China, has been charged with kidnapping. Police have said further charges are likely.
Early in the investigation, police said the last sighting of Bao was while she was out door-knocking for her work in Vickerys Rd, Wigram.
However, police have been unable to verify the sighting, which now appears to be a red herring.
On Wednesday, Detective Inspector Nicola Reeves said Bao was last seen in Trevor St shortly before 10am on the day she disappeared.
Her silver Nissan Dualis, registration PKT 556, left the street about 12.30pm. It was found in Iroquois Pl, Wigram about 10.45pm that day, hours after she failed to pick up her nine-year-old daughter from after-school care and was reported missing.
Police seized the Trevor St property under search warrant on Sunday afternoon, shortly after prospective buyers had looked around it during the open home event.
It's unclear what led detectives back to the property, and to make it the centre of their investigation.
On Thursday, Reeves said: "The investigation was exclusively a missing person enquiry up until Wednesday when it was elevated to a homicide investigation.
"Over the intervening period, police were investigating several possible lines of inquiry and as a result, certain locations became of interest as the available information evolved."
Prior to visiting the Trevor St property last Wednesday, it's believed Bao contacted the listing agent to let them know she wanted to show someone through, and to obtain the lock box code.
The property was due to go to auction this week, but the sale is now on hold.
Reeves previously confirmed a silver Mitsubishi sedan, registration DPH 101, belonging to the man accused of kidnapping Bao, was seen in Trevor St on the day she disappeared.
Stuff previously reported that last Wednesday, at 11.16am, Bao rang her friend Jin Tian and had a four-minute conversation with her.
During the conversation, she asked Tian how someone she was working with could transfer $600,000 (A$652,214) from China to pay cash for a house.
Two days later, Bao's cellphone was found on the Christchurch Southern Motorway, near Blakes Rd.
Late on Wednesday, Detective Inspector Nicola Reeves told a media conference she no longer believed the missing real estate agent was alive.
"We've always held grave concerns for her wellbeing, but as the week has progressed, and in particular developments over the last couple of days, we are now launching a homicide investigation," Reeves said.
She would not say why police now believe Bao was killed.
As police divers searched a river south of Christchurch, she appealed for sightings of the real estate agent's Nissan Dualis in the period between it leaving Trevor St and being found in Iroquois Pl.
Reeves would not say if the kidnapping accused was co-operating with police.
Police were not actively seeking anyone else in connection with Bao's disappearance, but investigators were "keeping an open mind" about the possible involvement of others.
Reeves said the Trevor St property remained of "significant interest" to the investigation.
She would not say if she believed Bao had been killed there, or taken from there.
"There is significant information and concern that's come from that address. I won't go into what I think has happened at that address, just that it is of significant interest to us and has certainly helped shape the investigation now."
Police have received more than 170 pieces of information from the public since news of Bao's disappearance was first reported.
It's understood investigators have relied on cellphone data to pinpoint of areas of interest as they search for the real estate agent's body.
CCTV footage they've gathered has also played a pivotal role in tracking the movements of Bao and her alleged kidnapper.
On Wednesday morning, officers in two inflatable boats slowly worked their way along the Halswell River near Neills Rd, southeast of Lincoln near Lake Ellesmere, as the investigation, dubbed Operation Helo, intensified.
A man in a wetsuit at the rear of one of the boats was monitoring what appeared to be an underwater camera.
A man who lived nearby told Stuff that police told another resident they'd tracked the movements of the kidnapping suspect along nearby roads through cellphone data.
Police searched the same stretch of water following the disappearance of Christchurch man Michael McGrath in 2017. David Benbow is accused of murdering McGrath, who remains missing.
In Christchurch, police also searched an area near Palmers Rd and the Avon River, New Brighton, on Wednesday morning.
