Investigators reviewing emergency calls from the morning of the terrorist attacks also have identified eight more recordings of emergency dispatches and 911 calls from the towers that had previously been overlooked.
Most of the bone fragments discovered over the weekend were found mixed with gravel that had been raked to the sides of the roof of the former Deutsche Bank building, which suffered extensive damage when the twin towers collapsed on Sept. 11, 2001.
Ellen Borakove, spokeswoman for the city medical examiner, said workers still had more than 100 yards of material to rake through and said she wouldn't be surprised by the discovery of additional remains.
"What they've cleared on the weekend was just a very small area. They still have quite a lot to go," Borakove said Thursday.
The building is contaminated with asbestos, lead and trade center dust. It is being cleaned before workers begin deconstructing it floor by floor in June.
Earlier this year, workers in the building found four additional human body parts, and they found 10 additional bone fragments on the roof last fall. In the most recent discovery, workers retrieved 82 samples, 74 of which proved to be human remains that will undergo DNA testing, Borakove said.
Some Sept. 11 family members have urged the Lower Manhattan Development Corp. rebuilding agency to have forensic experts search the building first. Many planned to ask Mayor Michael Bloomberg on Thursday to require a team from the medical examiner's office to be on the site at all times.
"This is an abomination that we are putting this on construction workers," said Sally Regenhard, the mother of a firefighter killed at the trade center.
The medical examiner's office has more than 9,000 unidentified remains from the 2,749 victims of the trade center attack. The remains are being are being stored in the hope that more sophisticated DNA technology will allow for identifications in the future. The remains of more than 40 percent of the people killed at the trade center have not been identified.
The newly discovered 911 recordings were identified on two previously overlooked tapes as investigators searched for the voice of a fire department official who died in the trade center.
The fire department said the recordings would be released after they are processed by the city law department. Roughly 130 calls were released Friday after the voices of the callers had been edited out. The voices of the fire and police operators who heard the calls for help were released after The New York Times and victims' relatives sued.
By Amy Westfeldt