Evacuated residents of Houston, the fourth-biggest US city, are only being allowed back in stages as Texas recovers from Hurricane Rita.
Texas' governor flew over flooded coastal areas on Sunday
Special routes have been set up to let people enter section by section, as power remains down in parts of Texas and schools and courts remain closed.
Plans are being made to avoid huge traffic jams in any future evacuation.
A search continues in Louisiana's wetlands where hundreds of people may have defied storm evacuation orders.
Rain and storm surges caused by Rita created flood levels of up to 2.7 metres (nine feet) in the Cajun country south of New Orleans.
More than 100 motor boats were refuelling in Abbeville before heading for search-and-rescue missions on Sunday.
"The flooding is still extensive," said emergency official Michael Bertrand in Vermilion Parish.
"We'll be going back through there to see if there's anybody left."
Louisiana Governor Kathleen Blanco inspected the hardest-hit parts of the wetlands by helicopter.
Impatient to return
Rick Perry, governor of Texas, appealed to people to delay their return.
The state, he said, had sustained about $8bn worth of damage from the hurricane but he predicted that most of the vital oil refineries had been spared and could resume production soon.
Last week's mass evacuation, involving nearly three million people, created traffic jams stretching as long as 100 miles (160km).
The BBC's Daniella Relph reports from Houston that residents are returning, but to order.
While it is a slow process, it is so far running smoothly though the city is still effectively closed for business.
But there has been some anger at the slow pace of the return. John Willy, the top elected official in Brazoria County, south-west of Houston, said he would ignore the staggered return plan.
"Our people are tired of the state's plan," he said. "They have a plan too and it's real simple: they plan to come home when they want."
The Texas governor is also now reviewing the state's emergency planning.
Getting up to three million people out of the way of the storm was extraordinary, he said, but he acknowledged that changes needed to be made.
Appeal for funds
The mayor of storm-ravaged New Orleans has said residents evacuated because of Hurricane Katrina can start returning to parts of the city.
Some parts were newly flooded by storm surges during Rita but Mayor Ray Nagin said he hoped to allow residents back to the Algiers district, which has power and water, as early as Monday.
The storm, he added, had delayed recovery efforts by another three to five days.
Governor Blanco asked on Sunday for at least $32bn in federal funds to repair damage to the state's infrastructure caused by Katrina and Rita.
The money, she said after meeting President George Bush in Baton Rouge, would be used to repair transportation systems and strengthen flood defences.