more than 2,200 immigrants

in a single day on Tuesday, the highest number in the agency's history, an ICE spokesperson confirmed.

The move comes as pressure from the White House has mounted to rapidly and massively increase arrests. ICE sources told NBC News that hundreds of the immigrants arrested were under ICE's Alternatives to Detention (ATD) program, which allows undocumented immigrants who are not considered a threat to public safety to be conditionally released. They are then monitored through ankle monitors, smartphone apps or other geolocation technology and regularly report to ICE offices.

ICE appears to have adopted a new tactic for at least some of the arrests. Immigration lawyers across the country say some of their clients in the ATD program have been told by ICE to show up for their appointments ahead of schedule through a mass message, but they have been arrested as soon as they arrive.

When NBC News asked for an

explanation for the arrests—several lawyers said their clients did not have final deportation orders—an ICE spokesperson did not immediately respond.

The arrests come after pressure from White House Deputy Director for Policy Stephen Miller, who threatened to fire senior officials at a meeting with ICE leadership last month if the agency did not make 3,000 arrests per day, according to two sources who attended.

President Trump has said he will deport "millions" of immigrants, and his border policy official Tom Homan said the administration will target the "most dangerous" immigrants.

But former ICE officials say

Trump's goal is unrealistic and that targeting only those with criminal records is putting undue pressure on the agency.

According to ICE data, the agency was using more than 20,000 ankle monitors by the end of last month. The same data shows that 98.5% of people in the ATD program show up for their appointments, making them easy targets for increased arrests.