Health experts say they are fearful that cases of positive COVID-19 cases could spike as thousands of people gather to protest police brutality.

New Jersey officials shut down many large protests can it came to reopening businesses, but have let the police brutality rallies keep going.

At least 1,000 people gathered in Princeton Tuesday evening – and only some of them were practicing social distancing. But almost all of the demonstrators were wearing masks.

“If not everybody was wearing a mask, I’m not sure I would stay,” said one demonstrator. “But it’s great. I don’t think I’ve seen one person without a mask.”

The rally in Princeton was one of many that took place in New Jersey Tuesday. Others took place on Monday and over the weekend – including one in Newark. Newark Mayor Ras Baraka attended the rally.

“I participated in that rally. I wore a mask, and let me tell you this; the next day, on Sunday, I got tested [for COVID-19.]” Baraka says

The mayor says that all people attending the protests should get tested.

“Do not assume that you did not contract the virus down there with thousands of people in close proximity,” he says.

Health experts say that the main concern is when protests turn ugly. They say that the chance of spreading the virus will jump.

“We’re going to have to watch this. I have little doubt that we will see some bumps from the protests,” says Dr. Howard Forman of the Yale School of Management.

Forman says that the spike could come within the next few days. He says that it is better that the gatherings are taking place outdoors.

“I’m sure that people have gotten this outdoors. It’s a much, much lower risk and maybe even lower still if people are wearing masks, maintaining social distance and so on,” he says.

Some of the protesters tell News 12 New Jersey that they are willing to risk COVID-19 exposure to come out for this cause.