A homicide investigation has been launched after a 10-month-old baby presented to Auckland's Starship Hospital with "non-accidental" injuries. 

Waitematā Police Detective Inspector Aaron Proctor confirmed at midday today the 10-month-old baby boy brought in to Starship Hospital on Wednesday evening has died today. 

"Sadly, the child passed away in hospital yesterday evening. A post-mortem is taking place today," Proctor said. 

"As such, the investigation has now been upgraded to a homicide inquiry." 

"Police inquiries are continuing, and any further updates will be provided when able." 

Yesterday, Proctor confirmed they believe the injuries were "non-accidental" and were now working to find out what happened. 

Proctor said the baby was presented to Starship on Wednesday evening with critical injuries. 

"Police believe the child's injuries are non-accidental and we are working to establish the circumstances surrounding this." 

Officers have been seen at a Vandeleur Ave, Birkdale, property on both Thursday and Friday. 

A blue tent was set up out the front, between the two properties. 

Proctor said the child remains in a critical condition in hospital and there have been no arrests at this stage.