Picture posted on Twitter shows police entering a building at the University of Oklahoma
(CNN) -- The University of Oklahoma in Norman briefly shut down Wednesday after a report of a possible shooting.
No evidence has been found of any shots being fired, and no injuries have been reported, school spokeswoman Catherine Bishop said.
After telling students to take shelter for more than 30 minutes, the school later announced that normal campus operations had resumed -- except at Gould Hall, the site of the reported shooting, "where additional checking is continuing," the school tweeted.
Gould Hall houses the university's College of Architecture.
Both the Norman and campus police responded quickly as did emergency personnel, the school tweeted, adding that the school's president, David Boren, is at the scene.
Boren told students the incident may have been a false alarm caused by a machinery backfire, independent student newspaper The Oklahoma Daily reported on Twitter.
Maj. Bruce Chan of campus police told CNN there was a report of shots fired in the Gould Hall area of campus.
The incident took place at around 11:20 a.m. local time (12:20 p.m. ET) while classes were in session.
Students and faculty were alerted via text.
On Tuesday, a gunman shot and killed a man at Purdue University in Indiana.
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