New York City ? The city plans to hire several more forensic experts to help hunt for human remains around the World Trade Center site after a cache of bones, believed to be those of Sept. 11 victims, was found there last month, a deputy mayor said Wednesday.

As many as 10 more forensic anthropologists will be hired temporarily to help in the next phase of the recovery project, which involves excavating more manholes and underground areas, tearing up parts of side streets and exploring rooftops of selected buildings near the 16-acre site, Deputy Mayor Ed Skyler said. Officials say that work could take up to a year.

Some 200 pieces of bone and other remains have been found since last month, when some of them were discovered in a manhole along the western edge of the lower Manhattan site. Officials said it had been paved over and forgotten when a service road was built there in the midst of excavating trade center rubble years ago.

Following that finding, city officials identified about 10 more manholes and pockets under the road and ordered them to be excavated immediately and sifted for remains. Workers are not quite halfway finished examining those cavities.