The number of Hurricane Katrina victims in Red Cross shelters is up to 45,000 and growing, the rescue organization reported Wednesday.
Some 250 shelters were open in the storm damaged area and the Red Cross had set up 15 emergency kitchens capable of feeding 350,000 people, spokeswoman Deborah Daley said.
"This is our largest mobilization in the history of the organization," she said.
"We are focused on providing the most elemental essentials ... food, shelter and water," she added.
Emergency response vehicles are also in the area providing food but they are operating from fixed bases since they cannot yet get into neighborhoods because of the damage, Daley said.
She said that it has been a major undertaking to get people and materials into the region and that it's going to take time.
Meanwhile, the Navy is sending four ships carrying water and other supplies to aid victims of Hurricane Katrina, while medical disaster teams and Red Cross workers from across the country converged on the devastated Gulf Coast region.
The Federal Emergency Management Agency urged people who evacuated before the storm to stay where they are.
"This hurricane has caused catastrophic devastation across areas of Louisiana, Mississippi and Alabama," said Michael D. Brown, head of FEMA. "We need everyone's cooperation to keep passable roads clear and to prevent those returning from placing additional burdens on the limited shelter, food and water in the heavily impacted areas."
He said returning residents could face blocked and washed out roads, downed power lines across highways, unsafe road crossings due to flooding and many other dangers.
The Federal Emergency Management Agency said medical specialists from Washington state were joining similar teams called in from Massachusetts, New Mexico, Ohio, North Carolina, Oklahoma and Florida to assist people in damaged areas.
Energy Secretary Samuel W. Bodman said Wednesday the Bush administration will also release oil from federal petroleum reserves to help refiners affected by Hurricane Katrina. The move is designed to give refineries in the Gulf Coast area a temporary supply of crude oil to take the place of interrupted shipments from tankers or offshore oil platforms affected by the storm.
Mississippi Sen. Trent Lott urged President Bush to visit the damaged region.
"Mr. President, the people of Mississippi are flat on their backs. They're going to need your help," Lott said in a call to Bush. "I urge you to come to Mississippi."
Bush was cutting short his Texas vacation and returning to Washington on Wednesday. He was expected to tour the storm-damaged areas later in the week.
Katrina came ashore Monday between New Orleans and Biloxi, Miss., inundating large areas of Louisiana, Mississippi and Alabama.
FEMA said it has 500 trucks of ice, 500 trucks of water and 350 trucks of military meals ready to eat scheduled for distribution in the next 10 days.
Four Navy amphibious ships were to leave Norfolk, Va., over the next few days for deployment on the Gulf Coast. The Pensacola Naval Air Station in Florida will be a base for the relief effort.
The Coast Guard received hundreds of calls for help and has assisted in the rescue of more than 1,200 people, spokesman Lt. Cmdr. Jeff Carter said Tuesday.
He said the Coast Guard had received reports that seven mobile offshore oil drilling rigs were adrift, and was working with companies on recovery and salvage plans.
The Coast Guard was conducting search-and-rescue missions and damage assessments by air and water, and was flying supplies to affected areas, Carter said.
In addition, Homeland Security Secretary Michael Chertoff - whose agency oversees the Coast Guard - has authorized the call-up of 550 Coast Guard reservists to help in recovery operations, Carter said.
In other developments:
-The Air Force said flooding and high winds damaged bases in Florida and Mississippi. Keesler Air Force Base in Mississippi suffered extensive damage to base housing, training facilities and industrial areas and flooding and downed trees also battered buildings at Homestead Air Force Base in Florida. At Camp Shelby in Mississippi, power had been knocked out, and fallen trees and flooding had done some damage.
-NASA reported that the Stennis Space Center in Mississippi and Michoud Assembly Facility in New Orleans were closed during recovery efforts.
-The Health and Human Services Department reported it had sent 27 pallets of medical supplies to Louisiana. These include basic first aid material such as bandages, pads and ice packs as well as blankets and patient clothing, suture kits, sterile gloves, stethoscopes, blood pressure measuring kits and portable oxygen tanks.