Security is so tight at the University of Phoenix Stadium that even the costume Katy Perry is planning to wear during tonight's half-time show has been checked. "Katy Perry's stage came in last night," a customs and border protection official tells ABC News. "We've got port-a-potties. We've got everything—food, hot dogs, hamburgers, the NFL paraphernalia, jerseys, everything." While Homeland Security director Jeh Johnson says there haven't been credible threats yet, "Our challenges in Homeland Security are evolving. We have more concerns about domestic-based acts of violence." Law enforcement officers are using scanners on everything that goes into the stadium, and they'll be wearing portable radiation detectors during the game and have bomb-sniffing dogs. In addition, some 30 miles of airspace over Phoenix will be shut down, and F-16s will be in the air. (More Super Bowl stories.)