New Orleans Mayor Mitch Landrieu said cleanup of trees and debris was under way in the storm-stricken city, but the lack of power was frustrating.
"Like everyone else, my patience is wearing thin," he said. "This is more than an inconvenience; it continues to be dangerous for everybody."
The (New Orleans) Times-Picayune reported the electric utility Entergy Corp. said only about 40 percent of New Orleanians had power, while the lights were on for about 46 percent of the people in Jefferson Parish about four days after Isaac hit.
The U.S. Department of Energy said more than 15,000 electricity workers from more than 24 states were assessing the damage and working to restore power.
WJBC-AM, Bloomington, Ill., reported the Woodford County Emergency Management Agency confirmed a tornado touchdown northwest of Benson that damaged a structure and another twister was reported near Toluca and Hopewell in Marshall County. Funnel clouds also were sighted near Varna and Panola, the radio station said.
The Federal Emergency Management Agency said it had more than 1,350 staff members working with storm victims in Louisiana and Mississippi. FEMA Administrator Craig Fugate stressed Saturday that people who fled their homes ahead of the storm should wait until officials determine it is safe before returning.
"As the flood waters begin to recede, I urge disaster survivors not to return home until local officials give the all clear," Fugate said. "There may be hazards that prevent you from being able to return home such as downed power lines. Roads and bridges may still be impassable.
"The federal team continues to work side by side with local authorities to assist governors of impacted states as areas are stabilized."
FEMA said it had transferred more than 1.4 million liters of water, 1.3 million meals and 28,800 tarps to Louisiana to be distributed to storm victims.
More than 5,700 National Guard soldiers and airmen in Louisiana, Mississippi, Alabama and Florida have been placed on active duty, with more than 33,600 additional Guardsmen available to support relief operations.
The Energy Department also has agreed to loan 1 million barrels of sweet crude oil from the Strategic Petroleum Reserve's Bayou Choctaw site in Louisiana to Marathon Petroleum Co. to address the short term impact on the company's refining capacity caused by Isaac.
The U.S. Coast Guard said it was still working with the maritime industry to respond to grounded ships and stranded barges in the Mississippi River but noted the channel is safe for all types of vessels.
The Los Angeles Times reported the Isaac-generated rain across the Mississippi and Ohio river valleys, but not enough to truly slake the region's drought.
"This by no means will be a drought-buster," National Weather Service spokesman Chris Vaccaro said. "But we'll take whatever rain we can get."
The National Weather Service said 3-5 inches of rain is possible across central Illinois this weekend.
Isaac, which was responsible for five deaths in Louisiana and two in Mississippi, dropped more than 8 inches of rain in Pine Bluff, Ark., and 6 inches in Stuttgart, Ark. The Chicago Tribune reported Greenville, in the southwestern part of Illinois, received about 6 inches of rain Friday.
Thousands of people in Jefferson Parish lined up Friday to pick up packages of food and basic necessities from the Louisiana National Guard. About 2,000 boxes of meals-ready-to-eat were distributed, along with 7,656 bags of ice and 4,400 cases of water.
Shelters closed Friday in Plaquemines Parish, outside the boundary of New Orleans' renovated $10 billion levee system. Many residents whose homes were flooded or destroyed boarded buses to go to shelters in Shreveport.
A voluntary evacuation was announced in Ascension Parish, 60 miles west of New Orleans, after Lake Maurepas flooded nearby homes. A parish spokesman said flooding there was worse than from Hurricane Katrina, which devastated the region in 2005.
Tropical Storm Leslie in the Atlantic could affect the East Coast sometime next week, forecasters say.