As plans were announced to encourage 180,000 residents to return home, the city's head of emergency operations revealed its flood-protection systems were now so weakened that just three inches of rainfall would trigger another disaster.
Former marine colonel Terry Ebbert said a heavy storm would precipitate fresh flooding throughout 'so many of the areas we've now emptied and are dry'.
Despite concern over the continued vulnerability of the city to another failure of flood defences, four neighbourhoods were earmarked for reopening in the next 10 days, including the historic French Quarter.
Around half of the city remains underwater and rescuers are still finding bodies. More than 800 people are now known to have died, the majority in Louisiana.
Safety officials warned that those preparing to enter New Orleans over the next few days did so at their own peril.
Conditions in the city remain fraught with polluted drinking water, a crippled emergency call system, few hospital beds, contaminated soil and virtually no food.
A two-page warning underlining the risks will be handed to residents who pass through the two checkpoints that guard access to the city. The leaflet states: 'Proceed with extreme caution. Standing water and soil may be seriously contaminated'.
However, the mayor of New Orleans, Ray Nagin, maintained it was vital the city returned to normality as soon as possible. Unveiling his plans to begin inviting more than a third of the city's population back over the next 10 days, he said: 'The sun is shining. We're bringing the city of New Orleans back'.
As many as 180,000 people could return within 10 days to a city that held 460,000 before Hurricane Katrina struck three weeks ago. Nagin reassured residents that enough troops and police remained to keep order.
Yesterday the first businesses, mainly bar and shop owners in the French Quarter began pulling down plywood used to board up their windows. Tomorrow eastern sections of the city will open, followed by the main central business areas. Ebbert, however, refused to commit to opening the French Quarter in the near future.
Estimates suggest more than 80 per cent of the city remains without electricity. In addition, the Environmental Protection Agency reiterated its advice to 'avoid all contact with sediment' that still smothers large swathes of the city. Other concerns relate to the fact just three hospitals in the region are operating.
Among the buildings destroyed by the disaster was Charity Hospital, the only one in the area licensed to handle serious traumas.
'When you place all those people back in the city without a health care infrastructure it is a risky proposition ... we're going to have a second disaster in this city,' said Peter Deblieux, an emergency physician. His concerns coincided with fresh accusations of ineptitude against Fema, the Federal Emergency Authority that botched the initial rescue mission of the region.
Now it is under attack for faltering in efforts to provide aid. Its emergency hotline, announced by President George Bush only last week, is being accused of being unable to handle the volume of calls from those caught up in the disaster.
