A senior Mexican government official announced Tuesday (April 23) that Mexico has returned 15,000 mostly Central Americans to their home countries in the past 30 days, Reuters reports.

Tonatiuh Guillén López, head of the National Migration Institute, held a press conference to address the situation, explaining that most of the migrants swept up in the deportations are from Guatemala, Honduras and El Salvador. According to Reuters:

A third of all migrants currently arriving in Mexico are minors and there are also now more than 1,000 Cuban migrants in the southern Mexican state of Chiapas and another 2,000 in the northern border city of Ciudad Juarez, Guillén [López] told reporters.

Last month, President Donald Trump threatened to close the border if Mexico failed to immediately halt migrants from reaching seeking asylum in the United States. In response to Trump’s threat, Reuters reports that Mexican President Andrés Manuel López Obrador decided to detain more migrants and limit their access to humanitarian visas. That has resulted in a bottleneck of caravans headed north. Earlier today (April 24), Trump tweeted a renewed threat to close the border.