A weakened Ike pushed northward Sunday after slamming into the Texas coast as a strong Category 2 hurricane, flooding seaside towns, cutting power to millions and paralyzing the oil hub of Houston. The giant storm left extensive devastation in its wake and officials had barely begun to assess the damage, which early estimates put in the billions of dollars. Ike, which idled a quarter of US crude oil production and refining capacity, swamped the island city of Galveston and hammered Houston, the fourth most populous US city. It shattered the windows of skyscrapers, showering streets with glass and debris, tore apart bus shelters and ripped metal sheets off buildings. “This hurricane has caused devastation across areas of Texas and Louisiana,” said David Paulison, administrator for the Federal Emergency Management Agency. According to an early computer-model estimate of damage by the insurance industry, Ike could lead to $8 billion to $18 billion in claims. Federal and state officials, including Homeland Security Secretary Michael Chertoff, are set to tour storm-damaged areas on Sunday. About 2 million people evacuated before Ike made landfall early on Saturday. Officials urged residents to stay away for now, but many have returned to survey the damage despite widespread power outages and gasoline shortages. “We've asked them not to come home but unfortunately we don't have the resources to totally blockade the county,” said Doc Adams, emergency management coordinator for Brazoria County.