UPDATE 3:57 p.m. ET

Donald Trump addressed attendees at a Republican event in California's Bay Area, while hundreds of demonstrators gathered outside the venue.

"That was not the easiest entrance I've ever made," he told the crowd, to laughter. "Oh boy, it felt like I was crossing the border, actually."

Trump said it was recommended that he cancel the speech and go back to Indiana, but he didn't want to "let these people down."

“It was fun. It was a little different,” Trump said of the entrance, later adding he had to get through “dirt and mud and under fences” to get in, and would do the same to get out.

Earlier, Trump was filmed entering the hotel at the back entrance to dodge the crowd. He had to go around a fence and step over a concrete barrier to access the hotel.

3:45 p.m. ET

A Donald Trump speech in California was delayed after protesters stormed the grounds of the Hyatt Regency hotel where the GOP frontrunner was scheduled to speak to state Republicans.

Protesters broke through the barricades outside the hotel in Burlingame, south of San Francisco, bearing signs against the candidate, and could be seen amassing at the front driveway before a line of police in riot gear.

Claudia Cowan reported on "Shepard Smith Reporting" that the activity became more heated after Trump arrived at the building.

Trump was filmed entering the hotel at the back entrance to dodge the crowd.

Watch the report above, and tune into Fox News Channel for ongoing coverage.