Police say a shooter scare at the University of Oklahoma may have been prompted by a “bogus” call.

Students were told to shelter in place after a report of possible shots fired at the library on campus prompted a massive police response in Norman. The university has an enrollment of around 26,600 at its Norman campus. An all-clear was later given as the police found no sign of a shooting or any other related injuries.

Authorities say they will still examine campus video footage to see if it shows more about what occurred.

There have been several cases of “swatting” or hoax calls to the police involving schools this year. There have been several actual deadly shootings this year as well, including one on another large college campus at Michigan State back in February.