A 22-year-old woman brought illegally to the US from Argentina at the age of seven has been arrested after speaking about her plight at a meeting.
Daniela Vargas was detained in Jackson, Mississippi, and could be deported without a hearing, her lawyer said.
She is among 750,000 people - known as "Dreamers" - allowed temporary work permits under an Obama programme, but her status lapsed in November.
President Donald Trump has given mixed signals on the future of the programme.
Ms Vargas's father and brother were detained on 15 February in Jackson. She hid in a cupboard for hours, but was eventually found by armed immigration officers before being questioned and released.
Then on Wednesday, she appeared at a press conference in Jackson City Hall, speaking of her deportation fears and aspirations to become a maths teacher, and calling for a "path to citizenship" for undocumented migrants.
After she left the event, immigration officials pulled her over in a friend's car and took her into custody.
Ms Vargas's lawyer, Abigail Peterson, said her status under the Deferred Action for Childhood Arrivals (Daca) programme had expired in November 2016, and she had applied to renew it in mid-February, after saving for the $495 (£403) application fee.
Daca provides a two-year reprieve from deportation and permission to apply for a work permit. Ms Vargas had been granted the protection in both December 2012 and November 2014, Ms Peterson said.
She said that Ms Vargas would be treated as a "visa waiver overstay" and as such could be flown to Argentina without an immigration hearing, the New York Times reported on Thursday.
Immigration and Customs Enforcement spokesman Thomas Byrd said on Wednesday that Ms Vargas was taken into custody in a "targeted immigration enforcement action'' after the agency verified that her Daca status had lapsed.
He said a federal immigration judge would "decide whether or not she is eligible for immigration relief".
Ms Peterson said detaining someone with a pending Daca application was "very unusual" and "mind boggling".
'Very, very tough'
A small number of "Dreamers" have been detained since Mr Trump came into office, and their cases are being closely watched.
Mr Trump's presidential campaign website said he planned to "immediately terminate" the Daca programme for those whose parents brought them to the US illegally.
But since coming into office he has said he finds the subject "very, very tough" and intends to show "great heart" in dealing with what he described as, in many cases, "incredible kids".
Last week, the Department for Homeland Security announced tougher enforcement of existing immigration rules, issuing memos expanding the list of undocumented immigrants prioritised for "expedited removal".
It said the new guidance does not affect Daca recipients, but gave no detail on the programme's future.