UPDATED 4.03PM The body of a newborn baby boy found at a reserve yesterday had no external injuries a post mortem has revealed.

Police said the baby was a newborn but they were unable to establish if the baby was still-born.

The baby was found wrapped in clothing by the mangroves of the Mona Ave Reserve in Mangere.

Police have released images of two distinctive pieces of muddy clothing the baby was found wrapped in and hope someone will recognise them.

The baby's body was found with the clothes at a reserve in Mangere Bridge. Photo / Supplied via police

The post mortem found the baby boy was either Maori or Pacific Island ethnicity and had likely been at the reserve for less than 48 hours.

The body of the baby was found on Thursday morning by a man walking his dog through Mona Reserve in Mangere.

Forensic testing was underway to help identify the mother or father but the results could take weeks.

Detective Senior Sergeant Karen Bright hoped someone recognised the items of clothing which included a singlet with "Samoan Culture - Our Pride and Joy" on the front and a pair of "Active" brand track pants.

Bright urged anyone who knows the mother to come forward as they believe the woman could have given birth recently and may need medical attention.​

Police were making enquiries in the Counties Manukau area and local visiting high schools.

"Our priority right now is finding the baby's mother," Detective Bright said.

"We want to get her support and medical treatment.

"Our focus... is all about locating mum."

She said police needed urgent assistance.

"Anyone who wishes to speak with us can do so in confidence and we would reiterate that our main concern at this stage is the welfare of the mother," said Bright.

"We will provide another update later today once further inquiries have been carried out.

"Anyone who wishes to speak with police can call Counties Manukau Crime Squad on (09) 261 1321 or contact Crimestoppers anonymously on 0800 555 111."

The baby was found wrapped in the clothing. Photo / Supplied via police

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