COSTA MESA (CBSLA.com) — Thousands of anti-Trump protesters clashed with drivers and police Thursday evening in Costa Mesa.

Trump was speaking to thousands at a rally at the Orange County Fairgrounds.

The group of about 3,000 protesters gathered just outside in the parking lot of the fairgrounds. They held signs, many of them profane, and Mexican and American flags to protest Donald Trump, the controversial GOP presidential front-runner.

The protest group spilled out into the streets near Fair Drive and Fairview Drive and blocked traffic in several intersections.

Stu Mundel reported overhead in Sky 9.

The group of protesters was described as “very large and very aggressive.”

Law enforcement was on scene in patrol cars and horseback.

Mundel witnessed at least one driver get surrounded. Several protesters jumped on the vehicle.

Officers were not being aggressive. They set up a line and told protesters not to cross it.

Police in riot gear working to clear protesters at Trump rally after police cars were damaged @CBSLA @KCBSKCALDesk pic.twitter.com/GrQm5qDgQ5 — Chris Ercoli (@CERCOLICBS) April 29, 2016

The officers were outnumbered “greatly,” Mundel reported. More officers were added to make sure the crowd obeyed orders.

On the ground, KCAL9’s Stacey Butler reported she was “in the middle of chaos.”

Major Costa Mesa street shut down. Protestors and police clash BREAKING@cbs2 pic.twitter.com/u0f6XQUwYe — Stacey butler (@StaceyCBS) April 29, 2016

Around 9:20 p.m., some protesters could be seen jostling a patrol vehicle. It was not clear if any police were inside the car.

Protesters broke the side window of at least one patrol car and the back window of another.

Protesters are damaging police cars after OC trump rally @CBSLA pic.twitter.com/beTV4mq7tL — Chris Ercoli (@CERCOLICBS) April 29, 2016

A smaller group broke off from the main group and began throwing rocks at vehicle near the on-ramp to the 55 Freeway on Newport Boulevard. Some protesters also sat in the road to keep cars from advancing.

KNX 1070’s Pete Demetriou reported one graffiti message written on a wall near the O.C. Fairgrounds read “1-8-7 Trump”, using the police code for a homicide.

As it appeared the crowds began to disperse, Mundel reported overhead that a fight broke out between several protesters and apparent pro-Trump forces.

A Trump supporter was punched several times and bloodied.

Seventeen people were taken into custody, according to police.