New details about the suitcases that contained the bodies of two children have emerged revealing that the suitcases were moved a year before being discovered.

The suitcases were moved in the second half of 2021 between different storage units at the same SafeStore Papatoetoe facility, according to a Stuff report.

A person with knowledge of the move told Stuff that there were dead flies and rats in the unit – but there was no smell or clues to raise the alarm.

A spokesman from SafeStore said the company did not want to comment "as the police have asked so as not to compromise any investigation in progress".

The bodies of the children, aged between five and 10, were found by those who had unwittingly bought the suitcases from the South Auckland storage unit as part of an auction for abandoned goods.

The police investigation into the case – launched after the grisly find on August 11 at a Manurewa property – saw Interpol called in.

The children's bodies had likely been stored at the Papatoetoe SafeStore storage facility for three to four years before being discovered, Detective Inspector Tofilau Faamanuia Vaaelua said at the time.

The SafeStore facility in Papatoetoe where a Clendon Park family reportedly purchased the contents of a storage locker that contained human remains, Auckland. Photo / Jed Bradley

A little over a month after the gruesome find, a 42-year-old woman was arrested over the death of the two children. She was found "hiding in an apartment" in Ulsan, a South Korean city.

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"Police arrested the suspect at an apartment in Ulsan on Thursday following a stakeout with tips on her whereabouts and CCTV footage," Seoul's National Police Agency said.

"The suspect is accused by the New Zealand Police of having murdered two of her children, aged seven and 10 then, in around 2018 in the Auckland area," the statement read.

"She's been found to have arrived in South Korea after the crime and has been in hiding ever since."

While being transported to Seoul by police, the woman was asked by journalists about the allegations, the Yonhap News Agency reported.

"I didn't do it," the woman, who covered her head with a jacket, said repeatedly.

A woman was arrested in Ulsan, South Korea, pursuant to two murder charges related to the bodies found in suitcases in Manurewa, Auckland. Photo / AP

After New Zealand Police issued the arrest warrant for the woman, the Seoul High Court granted an extradition arrest warrant for the woman.

An extradition review is expected to be conducted at Seoul High Court.

At this High Court hearing it will be decided if the woman will be extradited back to New Zealand.

"To have someone in custody overseas within such a short period of time has all been down to the assistance of the Korean authorities and the co-ordination by our NZ Police Interpol staff," police said in a statement today.

"Police would also like to acknowledge the overwhelming support from the public since the commencement of a very challenging investigation.