(AP Photo/Charlie Neibergall)

Donald Trump will hold a rally Thursday at the Flynn Center for the Performing Arts in Burlington, Vt., a charming art deco 1930s theater that holds 1,400 people. But there's a hitch.

Trump's campaign gave away nearly 20,000 free tickets — and at least 6,500 people have said they plan to attend, according to the Burlington Police Department.

"For fire and general safety reasons, the city’s Fire Marshal and the US Secret Service will impose strict attendance limits in conformance with the Flynn’s occupancy specifications," the Burlington Police Department said in a news release Wednesday. They noted it is "common" for political campaigns to oversell events, and people are welcome in the city. However, "if the information we have proves accurate, there is a likelihood that they will be unable to enter the Flynn Theater to attend Mr. Trump’s event."

So what does that mean? A lot of people, standing in line, attempting to get inside the venue when it opens at 5 p.m. Some are apparently supporters of Burlington's former mayor — Democratic presidential candidate Bernie Sanders.

Burlington Police Chief Brandon del Pozo told the Burlington Free Press he has concerns about safety.

“I wonder if the Trump campaign took into account the safety of the police officers who have to contend with large, dissatisfied crowds,” he told the paper. “This situation would place police officers in needless confrontations with citizenry.”

If jam band Phish, which was founded in Burlington and played their first gig at Nectar's, a bar a few steps down Main Street from the Flynn, gave away the same number of tickets it would be a different story, del Pozo told the Free Press.

“If Phish was holding a free concert at the Flynn and gave away 20,000 free tickets, we would cancel the event out of public safety concerns,” the chief said. “We are committed to accommodating the campaign because political speech is the very essence of the First Amendment.”