A crew of demolition workers discovered 74 bone fragments near the World Trade Center site over the weekend, the largest number of remains found since the end of recovery operations nearly three years ago and a sign that significant quantities of human remains may have gone unnoticed in sporadic searches over the years.

Most of the fragments were found mixed among roof ballast -- gravel -- that had been raked to the perimeters of the roof of the condemned Deutsche Bank building, officials said. The building, at 130 Liberty Street, stands just south of where the twin towers once loomed, and intensive work began there last month to prepare for its demolition.

The towers rose nearly 800 feet above the roof of the building, which was showered with debris and remains on the morning of Sept. 11, 2001. Because of extensive damage and contamination, the structure was deemed a total loss, but its demolition has been delayed by legal wrangling and concerns about environmental hazards.

The Lower Manhattan Development Corporation, which has taken control of the building, began the preliminary stages of demolition two weeks ago. That brought fresh scrutiny to the site, where small quantities of remains have been found occasionally since 2001.