Some homes may be without power for weeks.
Meanwhile, oil and natural gas production in the Gulf of Mexico that had been shut down last month before the hurricane has resumed in limited volumes, US Minerals Management Service said Wednesday.
Also, the Louisiana Offshore Oil Port, which handles about 12 percent of the nation's crude imports and is tied by pipeline to about half the nation's refining capacity, does not appear to have been damaged by Gustav.
Utility giant Entergy Corp., with 1.2 million customers in Louisiana, reported 674,036 outages among them Wednesday and said outages expanded into Arkansas overnight, where 86,440 customers were without power.
More than half of Entergy's 141,000 customers in New Orleans were without power and, Rod West, president and CEO of Entergy New Orleans, said some residents returning to New Orleans may have power in a day or two. It may be much longer for others.
The US Minerals Management Service said about 4 percent of oil production had been restored, and natural gas output stood at about 8 percent. Some companies with platforms in the western Gulf of Mexico said they'd restarted production in the past day.
The Energy Department said 22 major natural gas processing plants that had been shut down reported no major damage and are expected to resume operations when gas begins to flow.
Restoring power is one of the most significant challenges the plants are facing, the agency said.
The US Gulf Coast is home to nearly half the nation's refining capacity, while offshore, the Gulf accounts for about 25 percent of domestic oil production and 15 percent of natural gas output.
Anadarko Petroleum Corp., the largest independent deep-water producer in the Gulf of Mexico, said on Wednesday that it had resumed production at two of its eight operated platforms, though those facilities were not in the storm's path.
Exxon Mobil Corp. said that crews were returning to platforms and other offshore facilities not in Gustav's path. Those in the hurricanes path were to be inspected.
