Police have launched a double homicide investigation after a serious incident left two people dead in South Auckland.

The offender, or offenders, fled the scene before police arrived.

"At about 1.45pm, emergency services responded to reports of a woman unresponsive at an address on Gambare Place," police wrote on Facebook.

"Sadly, she was pronounced dead at the scene.

During a search of the property, police also discovered a dead man.

Cordons are in place on Mahia Rd and the public are advised to avoid the area.

A staff member at a bar in Manurewa's Southmall told The New Zealand Herald she saw "quite a few police" running past the venue towards the McDonald's carpark on the corner of Great South Rd and Weymouth Rd.

She said a customer told her they had seen "someone running around with a gun".

The Herald reports a body was lying covered in the middle of Gambare Place.

A resident of the street told the Herald the whole street was closed off as officers investigated incident.

"No cars are allowed, no children are playing outside today and the public has been asked to stop walking on the street and stay inside."

The incident prompted Te Haikura a Kiwa and Leabank Primary School to go into lockdown. Both have since lifted the restriction.

"We have come out of lockdown and all students, staff, and persons on-site are safely accounted for. Everyone did extremely well and responded to instructions," Leabank Principal Caroline McLeod posted on social media.

"A notice will be going out to parents/caregivers tonight to provide some more information on what has occurred today."