http://www.nytimes.com/2001/09/22/nyregion/22NUMB.html

City officials said yesterday that the number of people listed as missing and feared lost in the World Trade Center disaster, which had climbed as high as 6,333, could fall significantly because of problems with reports of missing people from foreign countries and other sources.

Mayor Rudolph W. Giuliani said the reports of missing foreign citizens, which had helped increase the number of those listed as missing and perhaps dead by about 1,000 over the last three days, probably involved many people who had been counted twice or who in fact were neither working at nor visiting the twin towers.

"It’s likely to go down," Mr. Giuliani said of the total. He added, "I don’t think anybody knows yet if that number is going to go back down to 4,000 or 5,000 or it’s going to remain at where it is when they all net out."

The city’s official number of those feared lost in the attacks has been followed by the public with enormous concern, for many have regarded it as a responsible approximation of how great the final death toll could be. The importance of the number is all the greater, officials acknowledge, because of the real possibility that the destruction at the site of the towers was so complete as to make identifying all victims an impossibility.

Ultimately, then, the final count of the missing could become the count of the dead.

As a result, the chance that there could be double-counting or other confusions involving the city’s numbers of the missing moved officials yesterday to urge caution in interpreting the daily accounting.

Just precisely how the city has been compiling its lists of the reported missing has been somewhat unclear from the first day after the disaster. Officials have, over time, created a kind of database of names and have resisted simply accepting reports of, in effect, lump sums of possible victims.

But names in the database have come from a variety of sources. Police Commissioner Bernard B. Kerik said that the city had compiled its list of the missing from the Red Cross, companies that had offices at the trade center and a number of police departments across the region. He said the multiple sources of reporting could have led to some duplication even beyond that involving foreign citizens.

"The numbers can change," Mr. Kerik said. "How much, we don’t know at this point."

The same person could be counted once in the total provided by Cantor, and then again as reported by family members.

It has become clear, though, that the question of foreign citizens has been the most problematic in efforts to keep the city’s count accurate. Over the last several days, the city’s list of the missing became inflated by what officials said were missing persons reports from consulates and embassies for countries including India and Israel.

But interviews with many consulate officials yesterday suggested that the lists of people they were collecting varied widely in their usefulness. For example, the city had somehow received reports of many Israelis feared missing at the site, and President Bush in his address to the country on Thursday night mentioned that about 130 Israelis had died in the attacks.

But today, Alon Pinkas, Israel’s consul general here, said that lists of the missing included reports from people who had called in because, for instance, relatives in New York had not returned their phone calls from Israel. There were, in fact, only three Israelis who had been confirmed as dead: two on the planes and another who had been visiting the towers on business and who was identified and buried.

In an effort to avoid further problems with the reports from foreign countries, Mr. Giuliani said the city had now created a separate list to deal with the names. He said that the new list, once it was sorted out, could come to include people who actually might be missing at the disaster site. But he and other officials indicated that that number was likely to be very small.

Indeed, Mr. Kerik said that the city’s early inquiry into the newest 1,200 reports of foreigners perhaps missing had left him skeptical. One country, he said, had reported 56 people feared to be missing at the site. After checking, officials now believe that none, in fact, had been in the buildings.

Experts were not surprised by the difficulty of creating and maintaining a reliable list of people feared lost at the scene of the trade center attacks.

David E. Garratt, director of the emergency support team at the headquarters of the Federal Emergency Management Agency, which is helping in the New York effort, said the challenges presented by the trade center disaster were, for him, unprecedented.

"When you are dealing with a building that has a large business community, a large number of foreign businesses and that is a tourist attraction where the tourists do not have to register by name, it is legitimately difficult to quickly and confidently establish a missing population," Mr. Garratt said.

To date, the city has confirmed 252 dead, of which 183 people have been identified. Of those 183, 39 of them are from the uniformed services, meaning firefighters, police officers and others.

But along with the dwindling confidence at the site that anyone will be found alive, there has been a growing awareness among rescuers and city officials of how hard it may well be to positively identify many of those who died in the collapses.

Any human remains, even if they are several parts from a single person, can be linked to a single person through DNA.

If the city has a sample of the victim’s DNA on file, from a toothbrush or a comb, then it is nearly certain that it can link a body or body parts to a missing person.

The challenge is finding the body parts in what could be 1.5 million to 2 million tons of debris.

"You just have to assume there will be some gap in between the number of missing and the confirmed dead," said Barry Scheck, a professor of law at the Cardozo School of Law and an expert on DNA testing.

But even establishing a reliable rough figure for the missing seemed at least briefly elusive yesterday. The mayor, for one, seemed to send conflicting messages.

At one point, Mr. Giuliani predicted that the number of missing might not change significantly. But then he said that it could drop to perhaps as low as 4,000 or 5,000 people from its current 6,333.