NEW YORK (AP) — The city has closed a facility where debris was sifted for Sept. 11 victims' remains, but the search won't end until after the World Trade Center site is rebuilt, a city official said Tuesday.

Ongoing construction around ground zero — including the dismantling of a toxic skyscraper that caught fire in August — could put off a complete search of areas believed to contain human remains for years, according to a memo by Deputy Mayor Ed Skyler.

"At no point in the near future would it be prudent to declare this search 'over,"' Skyler wrote to Mayor Michael Bloomberg.

The discovery of more than 80 bones in a manhole at ground zero in October 2006 prompted an expanded search of nearby rooftops, manholes and sewer lines for bone fragments of victims of the terrorist attacks. Hundreds of bones were found beginning in 2005 at the former Deutsche Bank tower across from the trade center site.

The city has found 1,772 bones and fragments so far. Seven victims have been identified from bones found in a service road at ground zero and on the roof of the bank building, Skyler said. More than 1,100 of the trade center victims have not been identified from the thousands of remains found after the attack.