U.S. Border Patrol agents in California arrested an alleged MS-13 gang member early Wednesday morning after he had illegally crossed the border into the United States, Customs and Border Protection (CBP) announced.

An agent from the San Diego sector was searching for "a group of illegal entrants" in a mountainous area around 12:45 a.m. Wednesday when he spotted a half-dozen men "near the border wall," according to CBP.

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A border patrol agent patrols along a construction site for the secondary border fence which follows the length of the primary border fence that separates the United States and Mexico in the San Diego Sector on August 22, 2019 in San Diego, CA. (Photo by Carolyn Van Houten/The Washington Post via Getty Images)

A border patrol agent patrols along a construction site for the secondary border fence which follows the length of the primary border fence that separates the United States and Mexico in the San Diego Sector on August 22, 2019 in San Diego, CA. (Photo by Carolyn Van Houten/The Washington Post via Getty Images) (Getty Images)

Upon questioning, all of the men acknowledged that they had illegally entered the U.S. and were arrested, authorities said.

While being processed at a nearby Border Patrol station, agents discovered one of the men was "a documented MS-13 gang member," CBP said.

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The man, a 28-year-old El Salvadorian national, and the five others -- three of whom were also from El Salvador, one from Mexico and one from Honduras -- will be sent back to their native countries, the agency said.

The latest danger haunting our border comes as the White House on Wednesday defended Vice President Kamala Harristravel, as she faces scrutiny for not having visited the overwhelmed southern border, amid her latest assignment from President Biden to handle the "root causes" of the surge in migration in recent months.

White House press secretary Jen Psaki on Wednesday during the press briefing was asked about the vice president’s recent travel to Chicago, as opposed to the southern border. While in the Windy City, Harris visited a local bakery.

"I would say the vice president was visiting Chicago to talk about COVID and the importance of communities getting the vaccine when it is available and accessible to them," Psaki explained. "While she was there, like many Americans, she got a snack. I think she's allowed to do that."

Fox News' Brooke Singman contributed to this report.