Bone fragments found more than four years after the World Trade Centre terror attacks on the rooftop of a nearby skyscraper are human.
The pieces were found in September by workers sifting through gravel on top of the former Deutsche Bank building.
The 41-storey building is being torn down after being struck by the Trade Centre's collapsing south tower.
New York's medical examiner will now try to identify the remains by extracting DNA.
This will be checked against a database of those killed in the September 11, 2001 terror attacks.
The city has recovered 19,964 pieces of human remains from the attack and identified 9,100 of them.
Some 2,749 people died at the trade centre but more than 1,100 have no identifiable remains.
Mary Fetchet, whose son died at the south tower, said the discovery reopened old wounds.
"It's just a reminder of the horrific nature of the event," she said.
"When you talk about identification of bone fragments, it just brings you back to what really happened that day."
The pieces were found in September by workers sifting through gravel on top of the former Deutsche Bank building.
The 41-storey building is being torn down after being struck by the Trade Centre's collapsing south tower.
New York's medical examiner will now try to identify the remains by extracting DNA.
This will be checked against a database of those killed in the September 11, 2001 terror attacks.
The city has recovered 19,964 pieces of human remains from the attack and identified 9,100 of them.
Some 2,749 people died at the trade centre but more than 1,100 have no identifiable remains.
Mary Fetchet, whose son died at the south tower, said the discovery reopened old wounds.
"It's just a reminder of the horrific nature of the event," she said.
"When you talk about identification of bone fragments, it just brings you back to what really happened that day."
