Two landmarks have been reached in the aftermath of the September 11th attacks on the World Trade Centre. The official toll of casualties - initially given as 6,500 - has dropped below 4,000 for the first time.
And the combustion at Ground Zero, which still sends plumes of smoke high over downtown Manhattan, has become the longest commercial building fire in US history.
Many US government officials - including Secretary of State Gen Colin Powell last week - still refer to 5,000 people killed in the attack on the twin towers. But yesterday New York mayor Rudolph Giuliani put the current - and still falling - official toll at 3,899. Every day the tally is reduced further as duplications and errors are discovered.
Last weekend alone, 200 names were eliminated and with more cross-checking the final count of those killed could eventually fall to 3,000, officials say. Many people initially listed as missing have in fact survived or were not in New York that day. Some individuals have been counted more than once, as in the case of a woman who was included under her maiden and married names. Diplomatic missions have also scaled back the number of foreign nationals thought to have been in the towers at the time.
With 189 people killed at the Pentagon and 44 in the crash of a hijacked plane in Pennsylvania, the overall total of casualties in the September 11th attacks on America now stands at 4,132. Still, perceptions of a much higher toll persist. On Saturday the radio talk show host Don Imus put the number of dead in the World Trade Centre attack at 6,000, during an interview with CNN's Larry King.
Meanwhile, work on recovering human remains in the wreckage of the twin towers is being hampered by intense heat from stubborn fires burning below ground. Smouldering debris containing tonnes of inflammable carpets, computers, office furniture and hydraulic oil tends to ignite when air ducts are opened by mechanical diggers scouring the 16-acre site.
Often steel beams dragged from the rubble glow red with heat. The smoke contains benzene, styrene, propylene and other chemicals, making the labour of rescue crews hazardous. Workers at the site complain of persistent coughs and headaches but residents in apartment blocks nearby have been reassured that they are in no danger. Jets of water are played day and night on the dwindling fires which are now concentrated in a small area beneath where the towers stood, but it may be early next year before they are finally extinguished.
Water alone cannot douse this kind of fire as heat cannot escape easily, experts say. A fire that began in a landfill in Centralia, Pennsylvania in 1962 is still burning. Fire officials have pumped in 750,000 gallons containing a heat-absorbing liquid known as Pyrocool, and the area of combustion is gradually being reduced by trucks hauling away still-smoking rubble.
Teams of ten firefighters working 12 hour shifts direct water deep into the rubble and spray jets high in the air to dampen dust sent up in clouds as rubble is removed and wrecking balls demolish adjacent buildings.
The most dangerous moments come when flames erupt without warning around earth-moving equipment as debris is moved and oxygen rushes in. While the emergency work at the site continues around the clock, there are growing concerns in New York that federal aid promised the city in the days after September 11th may be severely cut back.
President Bush initially promised $20 billion aid but only $11 billion has been allocated to New York in subsequent legislation.