Hurricane Ike pounded the Texas coast on Saturday, threatening to devastate towns along the Gulf of Mexico, shutting essential oil refineries and menacing Houston, the fourth-largest U.S. city. The enormous hurricane, roughly the size of Texas itself, may be the worst storm to hit the state in nearly 50 years and is set to make landfall within hours, the National Hurricane Center said. Ike's center, preceded by its strongest winds, bore down on the barrier island city of Galveston, driving a wall of water 20 feet high and sending huge waves crashing against a 17-foot (5-metre) sea wall built to protect the city after a hurricane in 1900 killed at least 8,000 people. The storm shut down 17 oil refineries, totaling more than a fifth of U.S. production, endangered a freighter at sea, and destroyed a pier in Galveston. The National Weather Service warned that people in coastal areas could "face the possibility of death" and officials said the vast storm could flood as many as 100,000 homes and send a huge wave across 100 miles of U.S. coastline. "Our nation is facing what is by any means a potentially catastrophic hurricane," said U.S. Homeland Security Secretary Michael Chertoff, warning that the storm surge, which may rise to 20 feet, could present the gravest danger. More than a million Texans heeded evacuation orders and headed inland, but officials said they were worried that many people had stayed in their homes. As the storm surge swelled onto Galveston Island, most downtown buildings were surrounded by water. Some residents who had ignored a mandatory evacuation order called to be rescued. They received no response because emergency workers were called off the streets, officials told the Houston Chronicle. Help was not expected until after the dangerous storm conditions subsided. "We don't know what we're going to find tomorrow," Galveston Mayor Lyda Ann Thomas told the newspaper. "We hope we'll find that the people who didn't leave here are alive and well. "Ike was a Category 2 storm with 110 mph (175 kph) winds, and could easily become a Category 3 hurricane on the five-step intensity scale with winds of more than 111 mph (178 kph) before making landfall. Forecasters warned it would send water surging up the Houston Ship Canal, the second busiest U.S. port, and that strong winds could seriously damage the glass-laden skyscrapers on Houston's skyline. Ike also forced waters inland and up a network of bayous that weave through the city, threatening to inundate neighborhoods. The costliest storm in U.S. history, Katrina, devastated New Orleans and other parts of the Gulf Coast, killing 1,500 people and causing at least $81 billion in damage.