The new identification happened weeks before the 25th anniversary. Photo: Getty Images

New York City has been working for more than two decades to formally identify each of the more than 2,600 people who died when the Twin Towers fell.

This week, the Office of the Chief Medical Examiner and the NYPD announced they formally identified a victim using genetic genealogy.

The process combines DNA testing with family research, the NYPD said.

The identification marks the 1,654th formal identification of a victim in the terror attacks. The adult woman has not been named.

NYPD Detective Gregory Paduano told ABC News: ‘The technology really wasn’t there 25 years ago.

‘There’s a lot of good future with genealogy.’

Dr Jennifer Odien, a forensic anthropologist, added: ‘Not every case is going to be able to go through genetic genealogy, but we do have DNA profiles that are not matching to our reference samples, so that’s the group right now that we’re focusing on and that hopefully is going to yield more positive results.’

47 DNA profiles could be identified using the new technology, Dr Odien said, but many victims of the attacks might never be officially identified.

Last year, the remains of three more victims of the 9/11 terror attack were identified.

Thanks to a DNA testing breakthrough, Ryan Fitzgerald, Barbara Keating, and a third woman whose family asked to remain anonymous were identified.

The attack on the World Trade Centre on September 11, 2001, saw two planes deliberately crash into the Twin Towers, killing more than 2,700 people.

Nearly 22,000 pieces of human remains, some as small as shards of bone the size of a fingernail, were recovered from the Ground Zero debris, NPR reported.

Having also suffered damage from fire, bacteria, pollution and other forms of degradation, DNA technology of the time was not able to uncover genetic profiles.

Ryan Fitzgerald, who was 26, was working as a foreign currency trader at Fiduciary Trust in the south tower on September 11, 2001.

He had called his family after the first plane hit the north tower to say he was OK and leaving his office.

She had worked as a public servant for 25 years and survived breast cancer twice, her obituary said.

She was known for visiting Saint Theresa Catholic Church every day, and would drive there and back in her red Sebring convertible.

Barbara was returning home to California after visiting family in Massachusetts.