The Trump administration’s efforts to convince illegal immigrants in the United States to voluntarily leave the country appear to be working, but a lack of information on the extent of the self-deportations from the government has made it difficult to know the extent of the operation.

“Tens of thousands” of illegal immigrants residing in the United States have used a Department of Homeland Security phone app to get paid to self-deport to their home country, a DHS official told the Washington Examiner.