Police say critical evidence was removed from the Lower Hutt property where baby Ru died in October and say the crime scene was cleaned before they arrived.
Toddler Ruthless-Empire Ahipene-Wall, also known as baby Ru, died in October just before his second birthday.
He had suffered violent injuries at a Poole Street home in the suburb of Taita before his death.
In a statement police said they believe items were taken from the house and that people seen using a grey-green 1994 Nissan Sentra with the registration TE6972 were responsible for removing them.
Police said the car travelled to and from the house three times after Ru was taken to hospital on October 22.
Police are appealing for information on these particular items:
They are:
• A Provision-ISR NVR5-8200PX+ DRV unit
• Eaton 5E UPS 650VA/360W power back up unit and 2 x NZ Outlets.
• Swatch of duvet cover
Police also said they wanted more information about a piece of fabric that was tied around Ru's neck when he was taken to hospital.
"Although not a direct cause of his death, the fact that such an item was around his neck is incredibly concerning, and we appeal for information from anyone who has seen this item or what it was used for," police said in a statement on Monday.
"We are continuing to piece together a timeline of the movements of persons of interest, who we are continuing to engage with, and of the movements of the Nissan.
"The cooperation of our three people of interest is vital to us understanding the truth of what happened to Baby Ru, and ultimately holding those responsible to account."
Baby Ru's initial unexplained death was upgraded to a homicide on October 26, when police revealed the post-mortem results showed he died due to blunt-force trauma.
"We believe that these injuries were not accidental," said Det Insp Nick Pritchard at the time.
It's understood he was injured up to 12 hours before he was found in an unresponsive state on October 22.
He was taken to Hutt Hospital but died shortly afterwards.
