Youth Day could be scrapped at the Canadian National Exhibition (CNE) after a series of fights forced the popular event to abruptly shut down, setting off what some called "sheer chaos" in the crowds.

Virginia Ludy, the CNE's general manager, said she was forced to shut down the event due to a dangerous "crowd dynamic," among a few groups of teenagers in the midway area. Video of the fights show swarms of people surrounding the fighters, while others rush away from the scene.

Ludy said some 70,000 people were at the Exhibition grounds, a large area of downtown land near the city's lake shore, so organizers who were monitoring the crowds had to power down rides and call in police around 9:30 p.m.

"You don't want to create panic and you don't want to create chaos," Ludy told CBC Radio's Metro Morning.

But, she said, organizers could not hesitate to close with patrons' safety at risk.

A line of police officers cleared the crowd at the CNE on Tuesday. (CBC)

Naomi Harris, who was visiting Toronto from Los Angeles, tweeted that she left the Ex as soon as she could after the brawls broke out. "It was sheer chaos," she wrote.

<a href="https://twitter.com/metromorning">@metromorning</a> I was at the Ex last night. It was sheer chaos. As an expat living in LA I was so out of here. No longer feel safe in Toronto. —@mapledipped

Kevin Proulx, who captured video of people running away from the fighting on the midway, described the scene as a "sudden stampede" on Twitter. He said he witnessed multiple fights break out.

But not everyone was happy with the abrupt end to their night out.

Tama Knight posted online that she felt closing the entire CNE was an over-reaction. "Most likely nothing would have happened," she tweeted, adding most of the fights appeared to be isolated events.

Police officers moved into the Exhibition grounds to stop several fights. The brawls, which involved dozens of people, sparked panic among the massive crowds that flocked to the Ex for Youth Day, which offers discounted tickets to those under 17.

Video filmed from one of the CNE's rides captured one of the fights as well as people running away from the scene.

CNE shut down because of this fight. <a href="https://twitter.com/hashtag/CNE?src=hash">#CNE</a> <a href="https://twitter.com/hashtag/CNEFight?src=hash">#CNEFight</a> <a href="https://t.co/dW0W2LChD7">pic.twitter.com/dW0W2LChD7</a> —@AliBinesh

Four teenagers were arrested in connection with the violence. Nobody was injured amid the skirmishes.

Someone also reported hearing the sound of gunshots to Toronto police, but officers found no evidence that a firearm was used.

Enhanced police, security force was already on hand

Ludy said organizers did their best to close the Ex in stages to reduce anxiety in the crowd, but said it can be hard to communicate with everyone about what's happening.

We're going to have to look at Youth Day, quite honestly. - Virginia Ludy, Canadian National Exhibition General Manager

"Often when these things happen there's a lot of rumours and a lot of speculation about what's going on," she said, noting the Ex stopped selling tickets earlier than normal on Wednesday night.

Ludy said there was already an enhanced police and security presence at the event before the trouble started.

Now, she said, organizers will have to review the Youth Day event to see if it will continue in the future.

"We're going to have to look at Youth Day, quite honestly," she said.

The annual event was also forced to close an hour early last year, though Ludy said that was because organizers wanted the large crowd — which was bigger and better behaved than this year's crowd — to be able to take public transit home.

On Tuesday night, police also closed several streets in the area to deal with the foot traffic leaving the CNE.

Among the people arrested, a 17-year-old was charged with drug possession, while two 16-year-olds were charged with assaulting a peace officer. One of the 16-year-olds was also charged with failing to comply with recognizance.

Police said on Wednesday afternoon that a 16-year-old girl was also arrested and charged with two counts of assaulting a police officer and one count of obstructing a police officer.

The CNE will be open as scheduled tonight.