The family of a 3-month-old boy who died after suffering injuries at his Southland home are finding it difficult to cope with the "terrible tragedy'', police say.

The boy died in Auckland's Starship Hospital early today after being transferred from Southland Hospital in a critical condition yesterday.

Police said the baby suffered serious injuries in a reported fall at his home in Riverton.

A post-mortem examination was carried out today.


Detective Senior Sergeant Mike Bowman said the police investigation was continuing with a "two-pronged approach'' - on behalf of the coroner and to determine any criminal culpability.

How the baby fell, and what injuries he suffered, formed part of the police investigation.

"A post-mortem is being completed today and this will assist us in building a picture of what has occurred,'' Mr Bowman said.

Police extended their sympathy to the boy's family.

"This is clearly a terrible tragedy and a very difficult time for them.''

Six police staff and a team from Environmental Science and Research (ESR) team were continuing a forensic examination at the boy's home.

Emergency services were called to the house at 7.35pm on Monday after reports that the boy had suffered serious injuries and was unresponsive.