NEW YORK (AFP) - Thousands of unidentified remains from victims of the September 11, 2011 attacks in New York will be taken Saturday to ground zero, where a memorial of the attacks has been erected.

The attacks - in which hijacked jetliners smashed into the Twin Towers, the Pentagon in Washington, and a field in Pennsylvania - killed some 2,753 at the World Trade Center, alone.

But only 1,115 of the bodies were ever identified, according to figures from the New York medical examiners office.

The unidentified remains will be moved to a specially-built repository under the National September 11 Memorial Museum "on Saturday morning," said Susan Dahill, communication director for the "Voices of September 11th," a group that works with some 800 families of victims of the attacks.

The mayor's office sent a letter to victims' families to announce the transfer, local media reported. An assistant press secretary told AFP further details would be provided later in the week.

Nearly 8,000 pieces of human remains - which authorities have been unable to match with the DNA of victims provided by families - will be moved in a "solemn, somber, respectful procession" of vehicles from the police, fire department, and the Port Authority of New York and New Jersey, the New York Times reported.

There will be no religions ceremony or service, nor will the event be attended by city officials, the newspaper added.

Dahill explained the event will only be open to family members of the victims, "because of the space limitation."

The museum opens to the public on May 21, though authorities have established a five-day tribute period starting May 15 specifically for family members, workers at the former World Trade Center, rescue workers from the attack, and survivors.

The re-built World Trade Center includes five new skyscrapers, the memorial, the museum, a metro stop, some 51,000 square meters of retail space, and a performing arts center.