Police are looking for sightings of a Nissan Sentra in relation to the killing of Lower Hutt toddler Ruthless-Empire Ahipene-Wall, also known as Baby Ru.
Baby Ru died last month just shy of his second birthday after suffering violent injuries at a home in Taitā, Lower Hutt.
Detective Inspector Nick Pritchard told media at Lower Hutt Police Station they were speaking with three people of interest.
The vehicle they are interested in was seen going to the Hutt Valley Hospital. It's a light coloured Nissan Sentra Sedan, which took Ru to hospital. The registration number is TE6972.
The vehicle returned to the address the baby had been living at and a person or persons removed property from the scene that was relevant to the murder investigation, he said.
"This property has been taken from the scene and has been concealed or disposed of," Pritchard said.
Police are building a timeline of movements of the vehicle, and are appealing for footage of it between the morning of 22 October through to mid-afternoon on 24 October.
The movements of the vehicle could be anywhere within the Wellington region, he said.
Police have already seized the vehicle and it has undergone forensic examination.
"The scene examination has been completed and items of relevance are undergoing forensic testing," Pritchard said.
Ruthless-Empire Ahipene-Wall Photo: Screenshot / Stuff
There were "varying levels of cooperation" from the three people of interest, he said. He believes they know they have the complete truth with what happened to Baby Ru, and he urged them to come forward with it.
All Baby Ru's injuries were to his head, Pritchard said.
"This poor child suffered a violent death," that could have been from a weapon, or slamming his head on a hard floor or table, he said.
He added: "To see this sort of violence against a young child, it's really hard to fathom."
Police are monitoring claims of what happened shared on social media, he said.
Pritchard would not confirm what items were undergoing forensic testing.
Police checked on the welfare of Baby Ru at a Waikato address in July this year, and there was "nothing adverse" found in that visit, Pritchard said.
Ruthless-Empire Ahipene-Wall, who was nearly two years old, died from violent injuries on 22 October.
He was taken to Hutt Hospital at 10.30am on 22 October in an unresponsive state, but efforts to revive him were unsuccessful.
Police earlier said they were looking into the background of all the individuals concerned, and were working with Oranga Tamariki and other family members to understand the history of Ru and the family.