Border Patrol spokesman Omar Zamora says Vargas was in custody Tuesday morning, but he had no other details.
Vargas had been in the border city of McAllen for several days as part of a vigil drawing attention to the plight of unaccompanied immigrant children and families coming into the U.S. illegally.
On Tuesday morning, Vargas tweeted: "About to go thru security at McAllen Airport. I don't know what's going to happen."
At the McAllen airport, Border Patrol agents stand beside Transportation Security Administration agents checking documentation, even for domestic flights.
In 2011, Vargas, who is from the Philippines, made headlines when he publicly declared that he was an illegal immigrant.
According to the immigrant advocacy group United We Dream, Vargas traveled to the Texas border to support the group's efforts to shine a light on the growing number of children who have fled Central America to escape violence.
Cristina Jimenez, the cofounder and managing director of United We Dream, told Business Insider that on July 5, she had invited Vargas to join her group for the vigil.
"It really was not apparent to either of us that this would be a problem," Jimenez told Business Insider.
Vargas, who just released a documentary titled Documented, told the Huffington Post that he was surprised by how much security was present in McAllen.
"They're everywhere," Vargas told The Huffington Post on Saturday. "Actually, as I'm talking to you, there's a border control van parked at the hotel I'm staying at."
In 2012, Vargas told "CBS This Morning" that after "coming out" as an illegal immigrant, he has traveled the country and met many others in his shoes.
"I'm a part of this growing movement of people who are coming out about their stories," he said at the time.
Vargas was part of the Washington Post team that won the Pulitzer Prize in 2008 for coverage of the Virginia Tech massacre. He had also interned for The San Francisco Chronicle and the Philadelphia Daily News, and was a senior contributing editor at Huffington Post.