Large numbers of Afghans crammed into trucks and buses in Pakistan on Tuesday, heading to the border to return home hours before the expiration of a Pakistani government deadline for those who are in the country illegally to leave or face deportation.

The deadline is part of a new anti-migrant crackdown that targets all undocumented or unregistered foreigners, according to Islamabad. But it mostly affects Afghans, who make up the bulk of migrants in Pakistan.