Universities in Texas and North Dakota evacuated their campuses on Friday after receiving bomb threats, with all students and staff removed and law enforcement agencies called in.
"At 8:35 am (1335 GMT), a male with a Middle Eastern accent called the university. He said he was with Al-Qaeda and that bombs would go off across campus in 90 minutes," University of Texas at Austin spokeswoman Tara Doolittle told AFP.
A decision was taken to clear the campus and the deadline passed without incident, she said, but local and national law enforcement agencies remain on site.
"The buildings are still evacuated, we are still making sure the campus is safe," Doolittle added. "We cannot at this stage say that this incident was a hoax."
Separately, North Dakota State University said it had received a bomb threat and had ordered all students and employees to leave campus by 10:15 am (1515 GMT.)