NEW ORLEANS — Rescuers along the hurricane-ravaged Gulf Coast pushed aside the dead to reach the living yesterday in a race against time and rising floodwaters, while New Orleans sank deeper into crisis, with Louisiana’s governor ordering storm refugees out of this drowning city.

Two levees broke and sent water coursing into the streets of the Big Easy a full day after New Orleans appeared to have escaped widespread destruction from Hurricane Katrina. An estimated 80% of the below-sea-level city was under water, up to 20 feet deep in places, with miles and miles of homes swamped.

“The situation is untenable,” Governor Blanco said. “It’s just heartbreaking.”

The number of dead was still unclear, a day after Katrina slammed the Gulf Coast with 145-mph winds. But one Mississippi county alone was believed to have lost as many as 80 people — 30 of them from a beachfront apartment house that collapsed under a 25-foot wall of water. And Louisiana said many were feared dead there, too, making Katrina one of the most punishing storms to hit America in decades.

New Orleans’s mayor, Ray Nagin, said hundreds, if not thousands, of people may still be stuck on roofs and in attics, and so rescue boats were bypassing the dead.

“We’re not even dealing with dead bodies,” Mr. Nagin said. “They’re just pushing them on the side.”

The flooding in New Orleans grew worse by the minute, prompting the evacuation of hotels and hospitals and an audacious plan to drop huge sandbags from helicopters to close up one of the breached levees. At the same time, looting broke out in some neighborhoods, the sweltering city of 480,000 had no drinkable water, and the electricity could be out for weeks.

With water rising perilously inside the Superdome, Ms. Blanco said the tens of thousands of refugees now huddled there and in other shelters in New Orleans would have to be evacuated.

She asked residents to spend tomorrow in prayer.

“That would be the best thing to calm our spirits and thank our Lord that we are survivors,” she said. “Slowly, gradually, we will recover; we will survive; we will rebuild.”

All day long, rescuers in boats and helicopters pulled out shell-shocked and bedraggled flood refugees from rooftops and attics. The Coast Guard said it has rescued 1,200 people by boat and air, with some placed shivering and wet into helicopter baskets. They were brought by the truckload into shelters, some in wheelchairs and some carrying babies, with stories of survival and of those who didn’t make it.

“Oh my God, it was hell,” said Kioka Williams, who had to hack through the ceiling of the beauty shop where she worked as floodwaters rose in New Orleans’s low-lying Ninth Ward. “We were screaming, hollering, flashing lights. It was complete chaos.”

Across Louisiana, Mississippi, and Alabama, more than 1 million residents remained without electricity, some without clean drinking water. An untold number who heeded evacuation orders were displaced, and 40,000 were in Red Cross shelters, with officials saying it could be weeks, if not months, before most will be able to return.

Emergency medical teams from across the country were sent into the region, and President Bush cut short his Texas vacation yesterday to return to Washington to focus on the storm damage.

Federal Emergency Management Agency’s director, Mike Brown, warned that structural damage to homes, diseases from animal carcasses, and chemicals in floodwaters made it unsafe for residents to come home anytime soon. And a mass return also was discouraged to keep from interfering with rescue and recovery efforts.

In New Orleans, the flooding actually got worse yesterday. Failed pumps and levees sent water from Lake Pontchartrain coursing through the streets. The rising water forced hotels to evacuate and a hospital to boatlift patients to emergency shelters.

Officials planned to use helicopters to drop 3,000-pound sandbags into the breach and expressed confidence the problem could be solved. But if the water rose a couple feet higher, it could wipe out the water system for the whole city, said New Orleans’s homeland security chief, Terry Ebbert.

In devastated Biloxi, Miss., areas that were not underwater were littered with tree trunks, downed power lines, and chunks of broken concrete. Some buildings were flattened.

The string of floating barge casinos crucial to the coastal economy were a shambles. At least three of them were picked up by the storm surge and carried up to 200 yards inland.

The deadliest spot yet appeared to be Biloxi’s Quiet Water Beach apartments, where authorities said about 30 people were washed away. All that was left of the red-brick building was a concrete slab.

“We grabbed a lady and pulled her out the window and then we swam with the current,” 55-year-old Joy Schovest said through tears. “It was terrifying. You should have seen the cars floating around us. We had to push them away when we were trying to swim.”

Said Biloxi’s mayor, A.J. Holloway: “This is our tsunami.”

Looting became a problem in both Biloxi and in New Orleans, in some cases in full view of police and National Guardsmen.

Outside the broken shells of Biloxi’s casinos, people picked through slot machines to see if they still contained coins and ransacked other businesses. “People are just casually walking in and filling up garbage bags and walking off like they’re Santa Claus,” a Super 8 motel owner, Marty Desei, said.

Insurance experts estimated the storm will result in up to $25 billion in insured losses. That means Katrina could prove more costly than record-setting Hurricane Andrew in 1992, which caused an inflation-adjusted $21 billion in losses.

Oil prices jumped by more than $3 a barrel yesterday, climbing above $70 a barrel, amid uncertainty about the extent of the damage to the Gulf region’s refineries and drilling platforms.

By midday yesterday, Katrina was downgraded to a tropical depression, with winds around 35 mph. It was moving northeast through Tennessee at around 21 mph, with the potential to dump 8 inches of rain and spin off deadly tornadoes.

Katrina left 11 people dead in its soggy jog across South Florida last week, as a much weaker storm.