Only 55 bodies had been found among the rubble of the World Trade Centre by early afternoon, New York time, the city's Mayor, Mr Rudy Giuliani, said yesterday.
Four survivors and 55 dead bodies had been recovered and "a few thousand people" were believed to be trapped in the ruins.
However, the death toll is expected to soar into the thousands as more rubble is removed by diggers and scores of dump trucks trying to clear south Manhattan of debris. The collapse of the remainder of the World Trade Centre late last night will further hanper rescue efforts. Rescue workers were cleared from the area before the collapse.
Earlier, rescuers could hear mobile phones ringing beneath the rubble as anxious relatives desperately called missing relatives in the hope that someone might answer.
The city's hospitals were preparing to take in huge numbers of casualties and said they were "absolutely mobbed" by blood donors. However, they said, relatively few people have been rescued from the disaster zone and treated for injury. "We so far have a body count of 55 people, about a half hour ago," Mr Giuliani said.
"We were able to take out another person two or three hours ago, a woman who was found alive and taken to the hospital, so now there are at least four people we have been able to take out."