Efforts to identify victims have been complicated by a number of factors.

Human remains were damaged in the plane crashes and fires caused by jet fuel, meaning the office had only portions of victims for DNA samples, Soler said.

Scauso added that because of the timing of the attacks, many firefighters were changing shifts, but some stayed to help, grabbing whatever extra gear they could find. This meant some first responders recovered were wearing uniforms with others’ names, complicating identification.

The World Trade Center site also had many more victims than the other 9/11 terrorist attack sites.

The remains of five of the 184 people killed when American Airlines Flight 77 crashed into the Pentagon were never identified because of similar conditions. According to the National Park Service, enough remains were recovered to use DNA, dental records and fingerprints to identify all 40 victims aboard United Airlines flight 93, which crashed into a field in Shanksville, Pennsylvania.

Remains from the World Trade Center have been packaged and sealed to help preserve DNA for testing in the years to come. Soon after the attacks, individuals were identified using fingerprints or dental records, but as time went on, when neither was available, the office turned to DNA. Officials were able to use new technology to extract DNA and retest the same remains.

“That’s why all these years down the road, we’re still getting new identifications, because we’re just continuing to retest and retry with every new technology that becomes available,” Soler said.

DNA technology has helped the office identify 1,495 victims since 9/11 – some solely with DNA and others with multiple methods – according to the medical examiner’s office.

Last year, the city announced that with the help of DNA, 24 years later, it had identified three new victims – Ryan Fitzgerald, a 26-year-old currency trader, Babara Keating, a 72-year-old who was aboard American Airlines Flight 11 from Boston to Los Angeles, and a woman whose family kept her identity private.

Soler said the new FIGG technology uses whole genome sequencing – which provides a way to read someone’s entire genetic code. It means investigators can make more potential matches to family members who are more distant relatives of the victim. Once those matches are made, the New York Police Department helps find relatives who are closer to the victims.