Thousands of people streamed off three college campuses Friday after bomb threats prompted officials to issue evacuation orders for schools in Texas, North Dakota and Ohio. The threats on the campuses ended as false alarms after tens of thousands of people followed urgently worded evacuation orders. The threats coming as violent protests outside U.S. embassies in the Middle East also stirred nervous tension among some students, and Texas officials acknowledged global events were taken into account.

The first bomb threat came around 8:35 a.m. to the University of Texas by a man claiming to belong to the terror group al-Qaida, officials said. The caller claimed there were bombs placed throughout the campus that would go off in exactly 90 minutes, but campus 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. UT President Bill Powers defended the decision not to evacuate sooner, in rather confusing fashion:

“It’s easy to make a phone call … the first thing we needed to do was evaluate,” Powers said. “If the threat had been for something to go off in five minutes, then you don’t have the time to evaluate, you just have to pull the switch.”

The delay worried some students, like Ricardo Nunez:

“What took so long? It should have been more immediate.”

North Dakota State University in Fargo was also a target. FBI spokesperson Kyle Loven said the university received a call at 9:45a.m. which included a “threat of an explosive device.” NDSU President Dean Bresciani said about 20,000 people were evacuated in a process “that largely took place in a matter of minutes.”

Lee Kiedrowski, a graduate student from Dickinson, N.D., said he was walking on the NDSU campus when he received a text message telling him to evacuate:

“The panic button wasn’t triggered quite immediately,” Kiedrowski said. “But there was definitely the thought that we live in a different world now, and with everything that’s going on with the riots at the U.S. embassies in the Middle East, your brain just starts moving. You never really know what’s going on.”

At Ohio’s Hiram college, staff received an emailed bomb threat around 4 p.m. and ordered everyone on campus to evacuate immediately. Hiram spokesperson Tom Ford said safety crews with bomb-sniffing K-9’s checked “room by room, building by building” on campus, which is about 35 miles southeast of Cleveland. About 1,300 students were evacuated.