Jose Antonio Vargas, an undocumented immigrant and Pulitzer Prize-winning journalist, who has become active on the immigration rights forefront has been detained by U.S. Border Patrol agents at a south Texas airport.

A spokesman for the U.S. Border Patrol Omar Zamora has confirmed that Jose Antonio Vargas is in custody as of Tuesday morning, but provided no other details.

According to the Washington Post, Vargas had been in McAllen, a south Texas city bordering Mexico, for several days prior to his arrest as part of a vigil to draw attention to the humanitarian crisis at the border.

The Rio Grande Valley has been the area of Texas in which a number of unaccompanied immigrant children and families have been coming into the U.S. illegally.

The number of Central American children at U.S. borders is expected to reach a record high this year, topping as many as 90,000 unaccompanied minors crossing the borders alone.

On Tuesday morning, Vargas tweeted: “About to go thru security at McAllen Airport. I don’t know what’s going to happen.”