Donald Trump was rushed off stage by the Secret Service during a rally in Nevada on Saturday but returned minutes later with a message that his campaign will “never be stopped.”

The presidential hopeful was mid-sentence at the event in Reno when two Secret Service agents surrounded him and quickly ushered him off stage. Security officials then leapt into the crowd.

It’s unclear exactly what triggered the swift reaction. Officials have not provided any details on arrests, but a man was filmed being pulled away by security and escorted out of the venue.

A few minutes later, Trump returned to the stage and thanked the agents.

He told the crowd that “nobody said it was going to be easy for us. But we will never be stopped. Never ever be stopped."

Trump’s campaign issued a press release shortly after the rally to thank his security detail for their "fast and professional response," but the statement didn’t offer any clarity as to what transpired.

Meanwhile, Democratic candidate Hillary Clinton spent Saturday rallying crowds in Florida under rainy skies and later appeared on stage beside pop superstar Katy Perry at a campaign-related performance in Philadelphia.

Americans will cast their ballots for the next U.S. president on Tuesday. According to figures crunched by The Associated Press, at least 41 million Americans in 48 states have already cast ballots in early voting.

With files from the Associated Press