He died six days later.
About 20 police are now working on a homicide investigation.
To date, charges have not been laid - however it is understood police are focusing on a small number of people connected to the toddler.
Oranga Tamariki have repeatedly refused to comment on the case, citing privacy and the police investigation.
Police were alerted to Malcolm's injuries by hospital staff who believed he had been deliberately harmed.
Detective Senior Sergeant Geoff Baber would not be drawn on the specifics of the case as it was ongoing.
"Police are continuing to piece together what has led to this child's injuries which we believe at this stage are non-accidental," he told the Herald earlier.
"Police are speaking to several people in relation to this matter and there is no further information available at this stage.
"Our thoughts are with Malcolm's family and whānau at this difficult time."
Malcolm's mother has refused to speak to the Herald.
"I have had legal advice and I will not be speaking to the media," she said when approached for comment.
Last month Children's Commissioner Judge Andrew Becroft announced a review into Oranga Tamariki's child uplift policies relating to care and protection issues for Māori babies.
It follows controversy over the attempted uplift last month of a young Māori mother's baby from Hawke's Bay Hospital.
The "thematic review" will look specifically at policies around Māori infants aged 0-3 months.
Judge Becroft said while the review would initially focus on the 0-3 months age group, he could not rule out extending the review to older children.
He said his office had a statutory mandate to investigate.
"If we didn't do it we would be asleep at the wheel," he said.
The same day Judge Becroft announced his review, Minister for Children Tracey Martin announced an internal inquiry by Oranga Tamariki into its processes specifically around the Hasting family's case.
