University of Pittsburgh police Tuesday evening sent out an emergency notification alert after an “incendiary device” went off outside the O’Hara Student Center during a debate on campus about transgenderism that caused protests.

There were no reported injuries. Medics were called to the area as a precaution. The Pitt News, quoting police, said the device was a “combination of a firework and a smoke bomb.”

The Pitt News reported that more than 250 people protested outside the O’Hara Student Center as Daily Wire host Michael Knowles debated libertarian journalist Brad Polumbo. The event called “Should transgenderism be regulated by law?” started around 7:30 p.m. The Intercollegiate Studies Institute sponsored the event, which was hosted by Pitt College Republicans.

Knowles, in a speech to a recent gathering of the Conservative Political Action Committee, drew backlash from some for saying that “transgenderism must be eradicated from public life entirely.”

Many of the protesters chanted and carried signs that read “No hate in Appalachia,” “Trans Rights are Human Rights” and “Trans Power.”

The event was posted on YouTube. Protesters could be heard yelling “Trans rights are human rights” when Knowles took the podium.

“There they are,” Knowles said. “That sounds like they’ve gotten into harmony. It’s not even melody anymore. I guess there was an opening act.”

A petition had previously circulated on Pitt’s main campus in Oakland calling for the Knowles event to be canceled.

At 8:18 p.m., Pitt police tweeted that “Several campus buildings in the vicinity of O’Hara Street will be closing early this evening. Residence Halls are accessible with proper identification.”

At 8:31 p.m. Pitt sent out a notification that Thaw Hall, Old Engineering Hall, Gardner Steel Center, Benedum Hall, University Club, Allen Hall and Space Resource Coordination Center were closed.

Knowles appeared to leave the event in an SUV around 9 p.m. Around that time, the crowd had dwindled down to 50. Police officers from Pittsburgh, Pitt and Carnegie Mellon University were on the scene.

At 9:39 p.m., the university sent out a notification that Nordenberg Hall and the William Pitt Union were locked down.

At 9:40 p.m., Pittsburgh police ordered people to leave the area and go home. The majority of the crowd dispersed.

At 10:23 p.m., the university tweeted that “all buildings are returning to normal operations.”

Click here for updates from the university.

Justin Vellucci is a Tribune-Review staff writer. You can contact Justin at jvellucci@triblive.com.