AUSTIN, Texas (AP) — University of Texas officials were defending their decision to wait more than an hour before evacuating due to a bomb threat, one of three such incidents reported at U.S. college campuses in a span of just a few hours.

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.