WASHINGTON -- Half of the nearly 3.5 million immigrants living in Texas are in the country illegally, according to a report scheduled for release today by the Center for Immigration Studies. Using the latest Census Bureau data, the center found that Texas has one of the fastest-growing immigrant populations of any state and that 50 percent of the state's foreign-born population -- slightly more than 1.7 million people -- are illegal immigrants. Only Arizona at 65 percent, North Carolina at 58 percent and Georgia at 53 percent had a higher proportion of illegal immigrants in their immigrant populations.