MCALLEN, Texas (AP) — Migrants who were temporarily allowed to live in the United States by using a Biden-era online appointment app have been told to leave the country “immediately,” officials said Monday. It was unclear how many beneficiaries would be affected.

More than 900,000 people were allowed in the country using the CBP One app since January 2023. They were generally allowed to remain in the United States for two years with authorization to work under a presidential authority called parole.

“Canceling these paroles is a promise kept to the American people to secure our borders and protect national security,” the Department of Homeland Security media affairs unit said in response to questions.

Authorities confirmed termination notices were sent to CBP One beneficiaries but did not say how many. They were urged to voluntary self-deport using the same app they entered on, which has been renamed CBP Home.

“It’s time for you to abandon the United States,” the Department of Homeland Security wrote to a Honduran family that entered the U.S. at the end of last year. The Associated Press reviewed the email received Sunday.

Others shared the same email on social media platforms.

Al Otro Lado, a nonprofit organization that provides legal aid to migrants, said some who received the revocation letters are from Honduras, El Salvador and Mexico.

CBP One was a cornerstone of the Biden administration’s strategy to create and expand legal pathways to enter the United States in an attempt to discourage illegal border crossings. By the end of December, 936,500 people had been allowed to enter with CBP One appointments at border crossings with Mexico. President Donald Trump ended CBP One for new entrants on his first day in office, stranding thousands in Mexico who had appointments into early February.

Trump has ended and revoked temporary status for many who benefited under Biden’s policies. Homeland Security said Monday that Biden’s use of parole authority — more than any president since it was created in 1952 — “further fueled the worst border crisis in U.S. history.”

Homeland Security said last month that it was revoking another form of parole for 532,000 people from Cuba, Haiti, Nicaragua and Venezuela who flew to the country at their own expense with a financial sponsor. It ends April 24.

The Trump administration has also announced an end to Temporary Protected Status for 600,000 Venezuelans and about 500,00 Haitians, though a federal judge temporarily put that on hold, including for about 350,000 Venezuelans who had been scheduled to lose TPS on Monday. TPS is granted in 18-month increments to people already in the U.S. whose countries are deemed unsafe for return due to natural disaster or civil strife.