Authorities in Southern California said early Friday that at least 20 people were arrested as protesters created havoc after a Donald Trump rally.

Costa Mesa police confirmed the arrests. Authorities said there were no major injuries and the big crowds had dispersed by 11 p.m. Thursday.

#OCSDPIO Post Trump Rally Protest over. Approx 20 arrests by Costa Mesa PD. No major injuries. Crowd dispersed by 11pm. No further updates — OC Sheriff, CA (@OCSD) April 29, 2016

Dozens of protesters were mostly peaceful as the Republican presidential front-runner gave his speech inside the Pacific Amphitheater. The crowds began to get rowdy as the rally was over and demonstrators took to the streets.

One Trump supporter had his face bloodied in a scuffle as he tried to drive out of the area. One man jumped on top of a police car, leaving its front and rear windows smashed and the top dented in and other protesters sprayed graffiti on a police car and the venue’s marquee.

Dozens of cars -- including those of Trump supporters trying to leave -- were stuck in the street as several hundred demonstrators blocked the road, waved Mexican flags and posed for selfies.

Police in riot gear and on horseback pushed the crowd back and away from the venue. There were no major injuries and police did not use any force. The crowd began dispersing about three hours after the speech ended.

As helicopters circled overhead, protesters at one point shut down the entrance to the 55 freeway along Newport Boulevard in Costa Mesa, the Los Angeles Times reported.

Earlier Thursday, a half-dozen anti-Trump protesters taunted those waiting to get into the area. Trump supporters surrounded one man who wave a Mexican flag and shouted “Build that wall! Build that wall!” – a reference to Trump’s call to create a barrier between the U.S. and Mexico to stop illegal border crossings.

At one point, seven women wearing no shirts and Bernie Sanders stickers over their breasts entered the square outside the amphitheater. They said they were protesting Trump's lack of engagement on issues of gender equality and women's rights.

"I feel like he wants to make America great again, but certainly not for women, for the LBGTQ community or for the lower class," said one of the women, Tiernan Hebron. "He has, like, done nothing to help with gender equality or women's rights or reproductive rights or anything."

Many protesters told the Los Angeles Times that they were drawn to the streets to rail against Trump’s policies on immigration and his remarks about Mexican immigrants.

“This is the anger people have against Trump,” Jose Cruz told the LA Times. “It’s not because he’s white, it’s because of what he’s said.”

Trump has drawn large crowds across the country as he has campaigned for the White House and some of his events have been marred by incidents both inside and outside these venues.

Earlier this week, a Trump rally in nearby Anaheim, California turned contentious when his supporters and counter protestors clashed, leaving several people struck by pepper spray. Trump was not present.

Trump has drawn large crowds to most of his campaign events, and Thursday was no exception. The Pacific Amphitheatre was filled to its capacity of about 18,000 and many hundreds more were turned away.

Ly Kou, 47, of Ontario, said she likes Trump because he has vowed to put the country first.

"It's obvious that America loves Trump," said Kou, who is from Laos, as she pointed at the waiting throng. "This thing about him being racist? Look around the crowd."

Trump was traveling from the rally site to the state's Republican convention in Burlington in the San Francisco Bay area.

The Associated Press contributed to this report.