University of Texas officials were defending their decision to wait more than an hour before evacuating due to a bomb threat.  The Texas school received the first threat around 8:35 a.m. from a man claiming to belong to al-Qaida, officials said. The caller claimed bombs placed throughout campus would go off in 90 minutes, but administrators waited more than an hour before blaring sirens on the campus of 50,000 students and telling them to immediately "get as far away as possible" in emergency text messages.  Authorities said they started searching buildings for explosives before the alert was issued.  The campus was deemed safe and reopened at noon with the remainder of Fridays classes being canceled with other activities scheduled on the campus to resume at 5 p.m.