The number of troops already in the area stood at 7,400 Thursday, a majority working in New Orleans to help restore order in a city descended into chaos.
"We continue to build our capability," Army Lt. Gen. Russel Honore told reporters from the Pentagon, the A.P. reported. "It's a trying situation at best, and the enormity of the task is significant."
At the Superdome in New Orleans, where troops have been trying to evacuate 25,000 people by bus to the Astrodome in Houston, reports of fights, trash fires and large, angry crowds trying to force their way from the arena were rampant.
Between 30,000 and 50,000 people are believed to be in the area hoping for a seat on one of the buses, CNN reported.
Inside the Superdome, which a lack of electricity has left stinking with the smell of rotting garbage and overflowing toilets, several dead bodies lay un-recovered on the grounds and in wheelchairs.
"We are out here like pure animals," the Rev. Isaac Clark told the Associated Press. "We don't have help."
A shot fired at a military helicopter also halted the efforts of an airborne ambulance service charged with flying sick and injured survivors out of the mass shelter. Acadian Ambulance service chief Richard Zuschlag said such flights had become too dangerous for his pilots, according to the AP.
Houston officials have agreed to take in 25,000 people from the New Orleans Superdome and have outfitted the Astrodome with phone lines in an effort to allow those arriving from Louisiana to communicate with family members.
San Antonio has agreed to take in 25,000 people.
Estimates of the death toll in New Orleans point to perhaps hundreds dead.
"Minimum, hundreds. Most likely, thousands," New Orleans Mayor Ray Nagin said when asked how many people had died in his city.
Late Wednesday, Nagin ordered New Orleans, once home to a half million people before Katrina's winds struck, evacuated. He said the city would likely be uninhabitable for the next two to three months.
In addition to the gasoline and sewage filled waters flooding the streets, looters and carjackers have also taken hold of the city, spreading the general sense of lawlessness.
"The truth is, a terrible tragedy like this brings out the best in most people, brings out the worst in some people," Mississippi Gov. Haley Barbour told NBC's Today show.
Mississippi officials reported Thursday the death toll there had risen to at least 185 dead.