Campaigners and leaders including the mayor of New York immediately called for the Philippine-born 33-year-old's release from detention in a Texas border town, some urging President Barack Obama to intervene.
Vargas was in the southern US state to join other lobby groups "to stand in solidarity with and humanise the stories of the children and families fleeing the most dangerous regions of Central America," the campaign group Define American said.
"This morning, Vargas attempted to board a plane to Los Angeles... Vargas did not make it through security at the airport," said Ryan Eller, campaign director of Define American.
"Our understanding is that he is currently being questioned by border patrol," he added in a statement.
"We are calling on President Obama and (Homeland Security) Secretary (Jeh) Johnson to exercise prosecutorial discretion and immediately release (Vargas) from Customs and Border Protection custody."
A spokesman for the US Customs and Border Protection agency, Joe Gutierrez, told AFP: "Yes, we have him in detention," but declined to give further details.
Vargas, who was part of a Washington Post team that won a Pulitzer Prize in 2008, revealed in a 2011 New York Times magazine essay that he was undocumented.
He was 12 years old in 1993 when his young mother put him on a flight in Manila to be raised by his grandparents in California, in the hope he could live the American dream.
New York Mayor Bill de Blasio said border agents had made a mistake.
"I stand in solidarity with journalist and advocate Jose Antonio Vargas - an exemplary man whose tireless work has helped raise awareness around the lives of millions of undocumented immigrants living on American soil," he said.
US authorities are currently dealing with a surge of unaccompanied and undocumented children coming over the country's southern borders with Mexico.
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
