NEW YORK, Oct. 20 (Xinhua) -- New York Mayor Michael Bloomberg on Friday called on city authorities to figure out why human bones were discovered at ground zero this week and discuss what other areas of the site should be searched for remains of the victims of Sept. 11 terror attacks.

    At an emergency meeting, the mayor urged agencies to "put them all together in a room to see what else we should go look at and why this wasn't discovered five years earlier."

    He also said that the city was planning to scour the site again for remains, examining other manholes and areas that might have been overlooked.

    The remains, some as big as arm or leg bones, were found by a Port Authority contractor working with a Consolidated Edison crew excavating a manhole at street level, a reconstruction official said.

    The location where the bones were found is next to where a podium is put up on Sept. 11 anniversaries for families to read the names of their loved ones.

    The area was roped off, and investigators sifted through dirt under a white tarp. The team of workers included forensic anthropologists who are overseeing the medical examiner's massive effort to identify Sept. 11 trade center victims.

    The discovery stirred up renewed anger and anguish among families of the dead. They called Friday for an investigation by Congress and state Attorney General Eliot Spitzer into the failure to completely remove the remains from ground zero.

    They also complained that officials rushed to clean the debris from ground zero without properly considering the remains.

    The group WTC Families for Proper Burial also called for ground zero construction to be halted until a proper search for remains can be completed.

    Meanwhile, police and forensic experts dug through a pile of rubble at the site Friday in search of more remains, an official said. The search involved additional material pulled from the manhole where the bones were found this week, and was expected to yield additional remains, said the official, who spoke on condition of anonymity because the official was instructed not to speak publicly about the matter.

    Construction work on several ongoing projects at the site, the Sept. 11 memorial, the 1,776-foot Freedom Tower and a transit hub, continued without interruption Friday, said Port Authority of New York and New Jersey spokesman Steve Coleman.

    During the excavation of the 110-story twin towers, which began the evening of the attacks and lasted for nine months, about 20,000 pieces of human remains were found. But the DNA in thousands of those pieces, many small enough to slip into a test tube, was too damaged by heat, humidity and time to yield matches in the many tests forensic scientists have tried over the years.

    Five years after 2,749 people died in the World Trade Center attack, families of about 1,150 victims still have not received word that their loved ones' remains were found amid the rubble. Enditem