A body, which police believe is Mamfredos-Nair's, was found at a Dairy Flat, rural Auckland, property this week, Detective Inspector Callum McNeill, of Waitematā CIB said on Saturday.
“While we still have to carry out formal identification procedures, from all of our inquiries to date we believe this is Jayden.”
Police charged two people, both 26, with murder on Saturday and have now arrested a third man, 20, and also charged him with murder.
The three are due to appear in the North Shore District Court on Monday.
Police are not ruling out further arrests.
Mamfredos-Nair was reported missing from West Auckland on April 24 last year, sparking a police investigation - which then turned into a homicide inquiry in August.
The 19-year-old had last been seen with two others at Birdwood Reserve in Rānui three days earlier, McNeill said last year.
The teen got into a 2022 black Toyota Hilux, later searched by police.
As part of the homicide inquiry - dubbed Operation Violin - a Dairy Flat address was thoroughly searched by police in October.
Jayden Mamfredos-Nair, who disappeared from West Auckland last April. A body found in Dairy Flat this week is understood to be the teenager's, police say.
They were seen using a ground scanning device, going over the driveway and grass. Police also sought the help of a body deposition expert who’d previously worked with the Australian Federal Police.
Further searching began at a Dairy Flat property on Wednesday, resulting in a body they believe to be Mamfredos-Nair's being found, McNeill said.
“This now brings an end to the search for Jayden, which has been ongoing for more than eight months.
“I would like to acknowledge the absolute determination of the investigation team, who from day one has never given up in their work to locate Jayden and to bring about answers for his whānau.”
Waitematā CIB Detective Inspector Callum McNeill pictured speaking to media after the disappearance of Jayden Mamfredos-Nair last year. A body believed to be the 19-year-old has been found in Dairy Flat.
He also praised the public who’d shared information with police or shared their appeals since Mamfredos-Nair went missing.
When the homicide inquiry was announced in August, Mamfredos-Nair’s distraught parents were seen holding back tears as McNeill spoke to media.
“We just want him back ... Let’s get him back, dead or alive,” Mamfredos-Nair’s mother said to media as she left the press conference.
The investigation team’s “thoughts and sympathies” were with Jayden’s whānau, McNeill said on Saturday.
“This has been a devastating ordeal for Jayden’s whānau, who are still coming to terms with the loss they have suffered.
“We hope that this brings them some closure, in knowing that their boy can now be returned to them so he can be laid to rest.”
