People carry belongings through a flooded street in the aftermath of Hurricane Katrina in New Orleans

Authorities in New Orleans are turning their efforts to collecting the bodies of what officials say could be thousands of people left dead by Hurricane Katrina and its aftermath.

On Sunday, U.S. Health and Human Services Secretary Michael Leavitt said it was evident that thousands died.  But six days after the storm, officials still do not know how many were killed.  Homeland Security Secretary Michael Chertoff says the nation must prepare for what he called "ugly pictures" as bodies are found. 

Rescue teams are also scouring the city for any remaining survivors after large-scale evacuations were completed at New Orleans' football stadium and convention center.  Officials say some people are refusing to leave their homes.

A group of residents waiting to board a U.S. Coast Guard helicopter to take them to the airport in New Orleans

New Orleans Mayor Ray Nagin says the strain of dealing with the disaster is taking a heavy toll on firefighters and police officers, with at least two of them committing suicide.  Separately, police shot and killed at least four people who fired on Army Corps of Engineers contractors on their way to repair a breached levee.

As criticism increased against what storm victims say is President Bush's slow response, Mr. Chertoff, Secretary of State Condoleezza Rice and Defense Secretary Donald Rumsfeld traveled separately to affected parts of the Gulf Coast Sunday. 

But Mr. Bush, who plans a second trip to the region this week, says victims can expect a "tidal wave of compassion" in coming days.

Some information for this report provided by AP, AFP, Reuters.