More than a million migrants who were allowed to enter the United States during the Biden administration may have their temporary stays revoked and be rapidly deported, according to an Immigration and Customs Enforcement document that became public Friday.

The Trump administration is powering ahead with efforts to ramp up immigration enforcement, opening up the possibility of targeting migrants who entered through Biden-era programs and invoking an obscure immigration statute to make it easier to deputize state and local law enforcement to arrest and detain immigrants in the U.

Many of the migrants under threat spent months waiting in Mexico, at migrant shelters or in rented rooms, in cities that are rife with cartel violence and kidnappings, in order to enter the US with permission.