New Zealand police have begun a homicide investigation after human remains were allegedly found stashed in suitcases that were bought at an auction in the country's largest city Auckland.

An undisclosed number of remains are believed to have been stored in suitcases auctioned as part of storage unit sale, and brought home by an unsuspecting family after their winning bid.

Residents at a home in South Auckland called police last Thursday after making the grisly discovery, police official Tofilau Faamanuia Vaaelua confirmed.

Police do not believe the family were involved in the suspected homicide.

"The priority for police is to confirm the identification of the deceased so that we can establish the full circumstances behind the discovery," Vaaelua added.

A post-mortem examination was underway and forensic investigators were trying to determine the number of victims, police said.

The auctioning of abandoned contents is a common practice for storage units with unpaid bills.

The owner of a storage unit in Papatoetoe, South Auckland, told news website Stuff that the business is cooperating with police in relation to the investigation.

Media outlet Newshub reported that police could be dealing with remains from multiple bodies.

Vaaelua added that police believe "there is no immediate risk to the public in regards to this incident".