Updated

Donald Trump’s planned rally Thursday night in Burlington, Vt., has local officials concerned about the massive crowds that could descend on the city.

The rally is being held downtown at the Flynn Center for the Arts, which seats approximately 1,400 people.

But local law enforcement say the Trump campaign informed them nearly 20,000 free tickets to the event were distributed -- and at least 6,500 of those people have confirmed a desire to attend.

Police have said once the venue reaches capacity, they will have to turn away those trying to enter. They also expect demonstrations to accompany Trump’s visit.

Burlington’s Democratic Mayor Miro Weinberger said in a statement that while he welcomes Trump to the city, “I am concerned, however, that the dramatic over-ticketing of the rally could mar Mr. Trump's visit.”

“I urge the Trump Campaign to take responsible steps to ensure the event proceeds smoothly and without incident,” the statement said.

Trump earlier tried to advise supporters of the situation. In a tweet, he said, “Massive crowd in VT tonight. Venue not big enough. Officials say NO to outside event and sound system. Arrive early!”

At past events, if the venue reached capacity, supporters were directed to an overflow space or outside.

The Republican front-runner is no stranger to large crowds. At a recent weekend rally in Biloxi, Miss., the candidate had over 10,000 people see him speak.