ANN ARBOR, Mich. (AP) — The University of Michigan says popping balloons may have sparked an “active shooter” alert at a building in the middle of campus.

In a statement late Saturday, the university says authorities received up to 20 calls about shots being fired at Mason Hall. The reports came during a nearby vigil for those killed in the mosque shootings in New Zealand.

Alerts issued by the school’s Department of Public Safety and Security around 5 p.m. told students who were near Mason Hall to “run, hide, fight.” About 40 minutes later, the university sent another alert saying there “does not appear to be an active threat to the community.”

Authorities confirmed there was “balloon popping activity” in the area where reports emerged about shots being fired. The school says there was no “malicious intent” behind the activity.