By Emily Stephenson and Amanda Becker

RENO, Nevada/PHILADELPHIA (Reuters) - Republican Donald Trump was rushed off stage by security agents at a rally in Reno, Nevada, on Saturday night after a false alarm as someone in the crowd shouted "gun" during scuffles with a man who held up a "Republicans against Trump" sign.

The incident occurred as Trump and Democratic rival Hillary Clinton crisscrossed the United States a late push to win over undecided voters and make sure supporters turn out enthusiastically on Election Day.

Two security agents seized Trump by the shoulders and hustled him backstage as police officers swarmed over a man in the front of the crowd and held him down and searched him before escorting him away with his hands behind his back.

Trump, seemingly unruffled, returned to the stage and continued his speech after a short time, saying "Nobody said it was going to be easy for us" and adding "We will never be stopped."

After being released, the man who was apprehended told CBS News Reno affiliate KTVN-2 that he was a Republican supporter who attended the rally to express his opposition to Trump.

"I came here with this sign expecting boos ... But it was just a sign," Austyn Crites said.

Crites said when he took it out, the crowd began to attack him, choking and beating him before "someone yelled about a gun."

After being held for a few hours' questioning and security and background checks, Crites said he was released, and that the police "did their job."

Crites said he wanted to contrast President Barack Obama’s reaction to a protestor during a rally a few days ago, in which he urged the crowd to respect the protester, with Trump's, saying he wanted “people to understand” the difference.

"I have nothing against Trump supporters," Crites told the station. "We are all registered Republicans and support many of the same candidates for local offices. I have serious concern against Trump," he added.

The Secret Service confirmed that the incident erupted when an unidentified individual in front of the stage shouted "gun."

"Secret Service agents and Reno Police Officers immediately apprehended the subject. Upon a thorough search of the subject and the surrounding area, no weapon was found," the Secret Service said in a statement.

The incident began when Trump noticed what he considered a heckler. Seconds later people near the stage began pointing at someone in the crowd near the front, and agents took Trump away.

In a statement, Trump thanked the Secret Service, Reno and Nevada law enforcement for "their fast and professional response."

Meantime, in Philadelphia, pop singer Katy Perry performed at a Clinton rally, the latest in a string of celebrity appearances aimed at getting out the vote among millennials.

"When your kids and grandkids ask you what you did in 2016, when it was all on the line, I want you be able to say you voted for a better, stronger, America," Clinton said.

Opinion polls show Clinton still holds advantages in states that could be critical in deciding the election. But her lead has narrowed after a revelation a week ago that the Federal Bureau of Investigation was looking into a new trove of emails as part of its probe into her handling of classified information while she was secretary of state.

A McClatchy-Marist opinion poll released on Saturday of voters nationwide showed Clinton leading by 1 percentage point compared to 6 percentage points in September.

A Reuters/Ipsos tracking poll on Saturday showed Clinton ahead by 4 percentage points nationally compared to 5 points on Friday, while an ABC News-Washington Post tracking poll had Clinton ahead by 48 to 43 percent.

COMPETING FOR FLORIDA VOTES

Both candidates spent time in Florida, considered one of the most hotly contested states. The 2000 presidential election was decided in Florida after a dispute over votes and recounting of ballots went to the U.S. Supreme Court, which ruled in favor of Republican George W. Bush over Democrat Al Gore.

The Real Clear Politics average of Florida opinion polls found Clinton with a lead of about 1 percentage point - indicating the race there is a virtual tie.

Trump spoke at a rally on Saturday morning in Tampa, Florida, where he continued to criticize Clinton for supporting the Affordable Care Act, also known as Obamacare, in the wake of an announcement that premiums are going to rise next year.

"It's not going to matter because if we win I'm throwing it out anyway," Trump said.

Shortly before Clinton took the stage in Pembroke Pines, Florida, rain poured down. People in the crowd waiting for Clinton at the outdoor rally remained in place, taking out umbrellas and fashioning garbage bags into head coverings.

"I'm thrilled to be here and boy is this a hardy group, rain or shine you are ready," Clinton said, her voice cracking with hoarseness.

She cut her speech short as she became soaked in rain, saying, "I don't think I need to tell you all of the wrong things about Donald Trump."

At the JFK library in Hialeah, Florida, people lined up outside for early voting. Nearby, supporters of both candidates waved signs and shouted slogans, urging passing drivers to honk their horns.

"We want someone to come in and clean house," said Cuban-American Ariel Martinez, 42, a Trump supporter.

Early voting began in September and the data firm Catalist estimates more than 30 million ballots have been cast in 38 states. There are an estimated 225.8 million eligible U.S. voters. Saturday was the final day for early voting in many Florida counties.

CHANGES IN PLANS

Trump and Clinton campaigns adjusted travel schedules for the next two days to states where they saw opportunity.

Trump told the crowd in Tampa that there would be a campaign event in Minnesota this weekend, although one had not previously been scheduled. Minnesota has not voted for a Republican since 1984. His campaign confirmed a rally scheduled for Wisconsin on Sunday has been canceled.

Clinton started the day by stopping by the West Miami Community Center, a Cuban American neighborhood, with telenovela star Jencarlos Canela, a Miami native of Cuban descent.

She then visited her campaign's office in Little Haiti where there is a large concentration of Haitian-American residents. Clinton was joined by Sybrina Fulton, the mother of Trayvon Martin, the unarmed black teenager who was shot dead in 2012 by a Sanford, Florida neighborhood watchman, George Zimmerman.

While Trump prefers large-scale rallies, Clinton has filled her campaign schedule with targeted appearances meant to court voters in specific demographics. Cuban voters have historically favored Republicans, but younger generations have shifted toward Democratic Party candidates.

In what was seen as an effort to defend typically Democratic turf, Clinton on Monday will campaign in Grand Rapids, Michigan, before returning to Pennsylvania for a rally in Philadelphia with President Barack Obama and first lady Michelle Obama, and former President Bill Clinton.

Trump is to make stops on Sunday in Iowa, Minnesota, Michigan, Pennsylvania and Virginia to try to steal away some states that have gone Democratic in recent presidential elections.

(Story corrects dateline to remove "N.C.".)

(Reporting by Emily Stephenson, Amanda Becker, and Luciana Lopez; Writing by Steve Holland and Chris Michaud; editing by Grant McCool, Mary Milliken and Simon Cameron-Moore)