(Adds mayor calling for voluntary evacuations of neighborhood, escapee quote, Ryan)
ORANGE, Texas/HOUSTON, Sept 1 (Reuters) - A week after Hurricane Harvey came ashore in Texas, rescuers pressed their marathon search for survivors on Friday in large pockets of land that remained flooded by one of the costliest natural disasters to hit the United States.
The storm has displaced more than 1 million people, with 44 feared dead from flooding that paralyzed Houston, swelled river levels to record highs and knocked out the drinking water supply in Beaumont, Texas, a city of about 120,000 people.
The Neches River, which flows into Beaumont and nearby Port Arthur, about 80 miles (130 km) west of Houston, was forecast to crest on Friday, and rescuers continued to pull people from nearby towns.
Tiana Kelly, 22, was waiting in a shelter in Orange, Texas, for a bus to transfer her to Louisiana, after being rescued from her flooded street by National Guard troops in a special high-water truck at 2 a.m. Friday.
"I was checking on my neighbor's dogs and I saw their flashlights, so I flashed my flashlight and they came and got us," Kelly said as she sat with her 11-month old son, Kalameet, in her arms. "They told us there was an eight-foot flash (flood) that was supposed to come."
Chemical maker Arkema SA said that a fire started on Thursday in a truck storing chemicals at a flooded plant 25 miles (40 km) east of Houston had burned itself out by Friday, but that more blasts were likely in eight other trucks storing the same chemicals in the coming days. Police were enforcing 1.5-mile (2.4-km) exclusion zone around the Crosby, Texas facility.
With three months remaining in the official Atlantic hurricane season, a new storm, Irma, had strengthened into a Category 3 storm on the five-step Saffir-Simpson scale, on Friday. It remained hundreds of miles from land but was forecast to possibly hit the U.S. territory of Puerto Rico, the Dominican Republic and neighboring Haiti by the middle of next week.
Harvey shut about a quarter of U.S. refinery capacity, much of which is clustered along the Gulf Coast, and caused gasoline prices to spike to a two-year high ahead of the long Labor Day holiday weekend.
With the presence of waterborne contaminants a growing concern, the National Weather Service issued flood watches from Arkansas into Ohio on Friday as the remnants of the storm made their way through the U.S. heartland.
Houston Mayor Sylvester Turner on Twitter on Friday called for voluntary evacuations of flooded homes in the city's northwestern Gessner neighborhood. He said he would consider a mandatory evacuation order if not enough people left the area.
Harvey roared ashore a week ago as the most powerful hurricane to hit Texas in half a century. It dumped unprecedented amounts of rain and left devastation across more than 300 miles (480 km) of the state's coast.
GASOLINE PRICES SPIKE
The national average for a gallon of regular gasoline has risen 17 cents since the storm hit, hitting $2.519 as of Friday morning, the highest since August 2015, according to motorists group AAA.
Several East Coast refineries have run out of gasoline, raising fears that travelers will face fuel shortages during the three-day holiday.
In major Texas cities including Dallas, there were long lines at gas stations, prompting state regulators to tell people they were sparking a panic and saying there were ample fuel supplies.
The storm came on the 12th anniversary of Hurricane Katrina, which killed about 1,800 around New Orleans. Then-U.S. President George W. Bush's administration was roundly criticized for its botched early response to the storm.
Signaling that he did not want to be seen as repeating those mistakes, President Donald Trump plans a second visit to the region on Saturday.
"Texas is healing fast thanks to all of the great men & women who have been working so hard. But still so much to do. Will be back tomorrow!" Trump said on Twitter on Friday.
Lawmakers will replenish a federal disaster relief fund to keep federal aid flowing to Hurricane Harvey victims, but full assistance will come from Congress in installments, U.S. House of Representatives Speaker Paul Ryan said on Friday.
"We won't fully know what all is needed for some time," Ryan said in an interview with radio station WCLO in his hometown of Janesville, Wisconsin. "But we do know that the cash drain is fast. And so we're going to have to do some quick responses."
Moody's Analytics estimated the economic cost from Harvey for southeastern Texas at $51 billion to $75 billion, ranking it among the costliest storms in U.S. history.
At least 44 people were dead or feared dead in six counties including and around Houston, officials said. Another 19 remained missing.
Tens of thousands crowded in evacuation centers across the region.
(Additional reporting by Richard Valdmanis, Marianna Parraga, Ernest Scheyder, Ruthy Munoz, Peter Henderson and Andy Sullivan in Houston, David Gaffen in New York, Jon Herskovitz in Austin, Texas, and Brendan O'Brien in Milwaukee; Writing by Scott Malone Jon Herskovitz; Editing by Bill Trott and Jonathan Oatis)