GALVESTON, Texas (CNN) -- Hurricane Ike's storm surge flooded Galveston's historic district early Saturday, sparked fires and knocked out power.
Heavy winds continued to pummel the coastal region more than four hours after the storm made landfall as a Category 2 storm.
It has since weakened to a Category 1, the National Hurricane Center said in its 9 a.m. ET update.
Galveston County's Emergency Management Coordinator John Simsen urged residents to be patient at a 7 a.m. briefing.
"We have a lot of work to do in terms of damage assessment," he said. "We don't understand yet what we're dealing with ...
"The last thing we want to do is put our citizens back into a situation where they may be in harm's way."
The storm flooded the historic district with 7 feet of water, which has since subsided to 4 feet, according to a Galveston county official. A foot of water flooded the city's main courthouse, where many people rode out the storm, Margaret Bunch said.
The storm cut off power to more than 4 million people in the Houston area after it made landfall at 2:10 a.m. CT on Galveston Island.
Ike's sustained winds eased to 90 mph, making it a Category 1 storm as it moved through Houston, the hurricane center said.
Hurricanes are ranked 1-5, with 1 as the weakest, on the Saffir Simpson scale of strength.
"Additional weakening is expected as the center moves farther inland, although Ike is expected to remain a hurricane through this afternoon," the hurricane center said.
Gas prices jumped in some regions of the country.
"The Department of Energy, the Federal Trade Commission and, I know, the state authorities will be monitoring the gasoline prices to make sure consumers are not being gouged," President Bush said during brief remarks at the White House Saturday morning.
Homeland Security Secretary Michael Chertoff will travel to Texas Saturday evening to review the federal response to Hurricane Ike, the Department of Homeland Security said.
Richard Kotrla in La Marque, Texas, about 8 miles from Galveston Bay, said early Saturday that Ike was "shaking this house pretty good."
"My gazebo is a pretzel," Kotrla said.
Houston officials warned residents to stay put because it was no longer safe to try to escape.
Those who stayed were largely in the dark.
Floyd LeBlanc of CenterPoint Energy Inc. said 1.8 million of the power company's customers -- or more than 4 million people -- in metro Houston are without electricity as high winds and heavy rains downed power lines. LeBlanc said 2 million customers represent about 4.5 million people.
"It's going to take several weeks to get all this power restored," he said. "We've been saying two to three weeks."
The hurricane caused fires and heavy damage around Galveston County, according to an initial assessment.
"Much of the Galveston Island is currently flooded, and there are several fires in that area," the Galveston County Office of Emergency Management said on its Web site. "Many roads in the county are impassable [because of] rising water and debris."
Some residents of Orange County -- which lies on the Louisiana state line -- were stranded on their rooftops and in attics because of storm surge, the county's emergency management office told the National Weather Service.
The city of Orange was flooded by the Sabine River, which runs along the state line, Beaumont emergency official Brad Peneffon said.
The coastal town of Bridge City was flooded by the Neches River and 9 feet of water was reported downtown, Peneffon said.
The storm surge from Hurricane Ike flooded 1,800 homes in Cameron Parish, Louisiana, and rescue officials couldn't get to them because of high winds.
Authorities urged evacuees not to return yet.
"We're telling people stay where you are, don't rush home. We're not out of the woods yet," Cameron Parish Sheriff Theos Dunhon said.
Three deaths in Texas have been attributed to the storm.
Authorities in Galveston imposed a curfew through dawn Monday.
Houston's Harris County is under curfew until 6 a.m. Sunday.
Galveston City Manager Steve LeBlanc said about 40 percent of the city's 57,523 residents chose to stay despite evacuation orders. "It's unfortunate that the warnings that we sent out were not heeded," he said.
A few more than 150 people were in a shelter of last resort, he said.
A fire broke out at a Galveston yacht basin, where boats are stored and fixed, said Galveston Fire Chief Michael Varela Sr., and firefighters were unable to reach it because the area was flooded with about 8 feet of water.
Varela said he was more concerned that new fires might break out elsewhere in the city, where many spots are impassable.
Brennan's, a popular restaurant in downtown Houston for almost four decades, burned down Friday night as Ike battered the city.
Earlier Friday, authorities rescued more than 120 people stranded by rising seas along the southeast Texas coast.
The Coast Guard said early Saturday that 22 people aboard a 584-foot Cyprus-flagged freighter that was adrift without power were safe after the storm.
About 200,000 residents fled low-lying areas of metro Houston. Roughly 3.5 million people live in the storm's impact zone, according to federal estimates.
"I've decided not to evacuate," said iReporter Matteu Erchull on Galveston Island. "We have a lot of faith in the sea wall, and we have boards on the windows. Most people on the island live on second or third stories, so they don't have to worry about the water so much."
Erchull later took shelter on the second floor of a Spanish restaurant in Galveston and said late Friday he could see fires burning in the northwest of the island.
(CNN's Mike Ahlers, Jeanne Meserve, Barbara Starr, Mike Mount and Jason Morris contributed to this report.)