By David Schepp BBC News Online's North America business reporter

It was a day not unlike that awful Tuesday eight months ago when two hijacked airlines struck the World Trade Center, causing its two 1,000-foot towers to collapse.

Mild temperatures combined with a gentle breeze and plentiful sunshine greeted onlookers to a ceremony that commemorated the end of the clean-up of the 16-acre site.

An empty stretcher is loaded into a waiting ambulance

What was different were the skies - not the stellar blue, they were on 11 September.

Rather, a stubborn morning fog burned off to a faint haze by the time ceremonies began at 1029 New York time, the precise moment when the second tower fell.

It was perhaps representative of the shroud that still hangs over New York's and the World Trade Center's futures following the attacks.

Pile of rubble

Thousands of onlookers ringed the rim of the World Trade Center site to watch the 20-minute observance that marked the end of the clean-up.

New York officials were in full force

At the site itself, dignitaries, including New York Senators Hillary Clinton and Charles Schumer, joined the hundreds of workers who had toiled away searching for bodies and cleaning up the mess.

Within months, they have turned a 10-storey pile of rubble into a vast, sterile dirt pit.

Thursday's ceremony was as much as tribute to them as it was to those who died.

Of the estimated 2,800 people who died in the fall of the twin towers, just over a thousand have been found and identified, including some of the 343 firefighters lost that day.

Honouring the workers

The sober event began with a call to arms. Members representing the more than a dozen agencies lined the 200-foot long ramp that descends into the cavernous seven-storey-high pit where more than a million tons of debris once stood.

In figures

2,823 people were killed 19,500 body parts collected 1,092 victims identified An additional 1,616 death certificates issued without a body at the request of victims' families 105 people still missing 1,642,698 tons of debris removed More than 3.1 million hours of labour used

Firefighters, rescue workers, police officers and others joined a procession that escorted an empty stretcher, symbolising all who perished but were not found at the World Trade Center, to a waiting New York Fire Department ambulance.

The ambulance was followed by a slowly moving lorry hauling the last steel girder from the south tower, which was cut down on Tuesday.

The huge steel beam, covered in a black shroud and draped with an American flag and flowers, moved slowly up the ramp and stopped while a bugle corps played taps and family members, rescue workers and government officials stood to attention.

Lastly, gentle applause greeted the workers as they followed the lorry from the site. The gentle clapping grew more thunderous as firefighters, including two of who survived but are still injured, exited the site.

Turning onto West Street, the trade centre's western boundary, the procession was greeted by cheers of "USA, USA, USA" by the thousands of uniformed New York police officers that lined the broad avenue.

Ultimate sacrifice

The ceremony was a symbolic end to the clean-up efforts. There is still much to do.

What is to become of the World Trade Center site will no doubt be debated extensively and heatedly over the next year as New York draws up its plan for a new trade centre.

A recently reopened department store looms over the pit

One small example of the forthcoming deliberations was present at the observance, where one man held up a sign that read, "Family input to a proper memorial is a must!"

But Thursday was not the day to begin the debate over a memorial or anything else that may be built where more than 2,800 souls perished.

It was instead a day to remember those who gave everything they had - some of who died doing it - and those who never had a chance.

And while New York's skies may not have been as clear as they were eight months ago, there is no doubt some spirits were lifted.