Three 9/11 victims have been identified using new DNA technology as the effort to return the remains of the dead to loved ones continues after nearly a quarter of a century.

New York City officials announced on Thursday, local time, that they had identified remains of Ryan Fitzgerald, a 26-year-old currency trader; Barbara Keating, a 72-year-old retired nonprofit executive; and another woman whose name authorities kept private at her family’s request.

The three were already among the thousands of people long known to have died in the Al Qaeda hijacked-plane attacks of September 11, 2001, and long listed among the names on the national memorial in New York City.

But these families, like many others, never previously knew of any remains of their loved ones.

The second tower of the World Trade Centre explodes

The second tower of the World Trade Centre explodes after being hit by a hijacked plane on September 11, 2001. (Reuters: Sara K. Schwittek)

In all, nearly 3,000 people were killed when the hijackers crashed jetliners into the World Trade Center’s twin towers, the Pentagon and a field in south-west Pennsylvania.

More than 2,700 of the victims perished in the fiery collapse of the twin towers, and about 40 per cent of those victims have not had any remains identified.

The new identifications were made through now-improved DNA testing of minute remains found more than 20 years ago amid the wreckage, the city medical examiner’s office said.

“Each new identification testifies to the promise of science and sustained outreach to families despite the passage of time,” chief medical examiner Dr Jason Graham said in a statement.

“We continue this work as our way of honouring the lost.”

Ms Keating’s son, Paul Keating, told media outlets he was amazed and impressed by the enduring endeavour.

“It’s just an amazing feat, gesture,” he told the New York Post.

The little girls who died on 9/11

It’s been two decades since a group of hijackers killed almost 3,000 people. On that day, one family thought they were embarking on a trip of a lifetime to Australia.

He said genetic material from part of his mother’s hairbrush was matched to DNA samples from relatives.

A bit of his mother’s ATM card was the only other trace of her ever recovered from the debris, he said.

Barbara Keating was a passenger on the Los Angeles-bound American Airlines Flight 11 when hijackers slammed it into the World Trade Center.

She was headed home to Palm Springs, California, after spending the summer on Cape Cod, Massachusetts.

Ms Keating had spent her career in social services, including a time as executive director of the Big Brothers Big Sisters of South Middlesex, near Boston.

In retirement, she was involved in her Roman Catholic church in Palm Springs.

Mr Fitzgerald, who lived in Manhattan, was working at a financial firm at the World Trade Center, studying for a master’s degree in business and talking about a long-term future with his girlfriend, according to obituaries published at the time.

The New York medical examiner’s office has steadily added to the roster of 9/11 victims with identified remains, most recently last year.

The agency has tested and retested tens of thousands of fragments as techniques advanced over the years and created new prospects for reading genetic code diminished by fire, sunlight, bacteria and more.

It said it would continue to retest in the future.

“We hope the families receiving answers from the Office of Chief Medical Examiner can take solace in the city’s tireless dedication to this mission,” New York Mayor Eric Adams said in a statement.

AP