US Secret Service and local police apprehended a suspect at a Donald Trump campaign rally on Saturday after someone in the crowd shouted “gun” but no weapon was found.
In a statement, the federal agency said an investigation was continuing, but US media in Reno reported that the Reno Police Department had released the suspect.
Mr Trump was bundled off stage by security officers after an apparently false gun scare during a campaign appearance.
US media cited law enforcement sources reporting that no gun had been found after a cry of alarm in the crowd, and Trump swiftly resumed his speech in Reno, Nevada.
The 70-year-old Republican tycoon reappeared just minutes after being led away by three Secret Service officers, who shielded his body with their own.
Minutes later, he reappeared to cheers, declaring: “Nobody said it was going to be easy for us, but we will never be stopped, never ever be stopped.
“I want to thank the Secret Service. These guys are fantastic. They don’t get enough credit. They don’t get enough credit. They are amazing people.”
Just before the fracas, Trump could be seen shielding his eyes from the lights in order to peer into the crowd as a struggle broke out.
There were signs of a fracas in the audience as the agents led Trump away, but once a suspect was in custody Trump returned to resume his stump speech.
Television footage showed a suspect pinioned on the ground by officers and searched, before he was led away by local law enforcement, including an armed response team in tactical dress with rifles.
Trump appeared unrattled and spoke with his usual self-confidence, finishing his planned remarks and accepting applause before returning to his campaign plane safely.
“I would like to thank the United States Secret Service and the law enforcement resources in Reno and the state of Nevada for their fast and professional response,” he said in a campaign statement.
Reporters at the venue had earlier cited unnamed local law enforcement sources and witnesses in the crowd as saying there had been a report of a gun among the Trump supporters.