(CNN) At least four people at a Bernie Sanders rally in Oakland rushed the stage Monday evening, spurring Secret Service agents to jump onto the raised platform and protect him.

The Democratic presidential candidate was uninjured and continued speaking, but not before several agents hugged him and pushed him away from the microphone. The identities of the individuals, who yelled as they approached the stage, were not immediately known. They were apprehended and led away by Secret Service from the podium at the Frank Ogawa Plaza, where the rally was being held.

After the events of Monday night in Northern California, Sanders spokesman Michael Briggs said, "It was handled professionally by the Secret Service."

An animal rights group, Direct Action Everywhere, claimed responsibility for the disruption in a press release.

"Activists do not protest at Bernie Sanders rallies in opposition to Sanders himself, but rather to pull Sanders in their direction," the group's press release said. "Sanders' opponent Hillary Clinton recently released a campaign platform on animal issues, although it stops far short of what activists would like to see. Activists expect Bernie Sanders, the progressive candidate, to support more radical action to provide animals not just with improved conditions but with legal rights to be free from harm."

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