Former President Donald J. Trump was escorted off the stage by Secret Service agents and into his motorcade just minutes into his rally on Saturday in Butler, Pa., after a series of pops that sounded like gunshots rang out.

The exact source of the noises was unclear, but Mr. Trump’s ear appeared to be bleeding as he was rushed off the stage.

Mr. Trump had been showing a chart of numbers about border crossings, which his audiovisual staff placed on screens above the stage, when the apparent shots rang out.

The former president ducked quickly after the noises began, with the sound coming from the bleachers to the left of where he was standing at a lectern. The noises came in two groups, and smoke rose from that section of the bleachers.

As members of the crowd began screaming, Mr. Trump was tackled by Secret Service agents. Officials shouted for the crowd to duck and cover, whisking members of the news media off the press riser where they had been watching Mr. Trump’s speech.

After a brief pause, Mr. Trump rose, surrounded by a group of uniformed Secret Service members. He pumped his fist to the crowd, and then was rushed off the stage and ushered into his motorcade, which quickly left the venue, the Butler Farm Show.

Steven Cheung, a Trump spokesman, said former Mr. Trump is “fine and is being checked out at a local medical facility.” He added that Trump “thanks law enforcement and first responders for their quick action during this heinous act.”

After he departed, a group of officials wearing camouflage escorted someone off a set of bleachers to the left of the podium where Mr. Trump was speaking. Police officials began cordoning off the area with crime-scene tape as the rally’s attendees began clearing out, and blood was visible on the bleachers.

The Secret Service asked members of the news media to leave roughly 20 minutes after Mr. Trump left the stage, declaring the rally site a crime scene.

Representatives for the Trump campaign did not immediately respond to requests for comment. The U.S. Secret Service and other law enforcement agencies did not immediately respond to requests for more information.

President Biden told reporters in Delaware that he had not yet been briefed on the incident at the Trump rally.

Those who attend Mr. Trump’s campaign rallies are subject to security screenings. They are required to enter through metal detectors, and their bags and possessions are searched for weapons and a large number of banned items.