President Trump’s drastic reshaping of immigration enforcement toward a goal of deporting millions has led to nearly 23,000 arrests and 18,000 deportations in the past month, federal data shows.

Arrests inside the country are up sharply relative to the Biden administration, but they are below the levels seen when immigration agents made a show of force at the start of Mr. Trump’s term.

Deportations have continued to lag. As a result, 4,000 more people are sitting in detention facilities than when Mr. Trump first took office. An additional 3,000 people who were detained have been released back into the country.

The administration began its increased enforcement operations shortly after Mr. Trump was inaugurated, and ICE was quick to publicize the number of immigrants caught in its operations each day. People booked into detention by ICE — a rough measure of arrests — peaked at 872 people per day in late January before falling to just under 600 people per day in the first three weeks of February, data shows.

This is a significant escalation from the Biden administration: ICE arrested and detained about 255 people each day last year. It also reveals the extent of a shift in immigration priorities under Mr. Trump to increase enforcement in the interior of the country.

Deportations have not kept pace with arrests. ICE deported an average of 600 people a day in mid-February, the latest data available, compared with more than 750 people a day in the 12 months through November.

The drop in deportations is due in part to a simultaneous change in border policy. During the Biden administration, a majority of people detained and deported were arrested crossing the southwestern border. But the Trump administration moved to quickly close the border, ending the asylum process and other Biden-era programs that offered migrants humanitarian relief.

Now, border agents are arresting far fewer people than last year and sending fewer migrants to ICE for detention and eventual deportation. (It is not clear how many people are being removed directly from the border, since that data has not been published since Mr. Trump took office.)

Even though arrests at the border are down, the aggressive push to detain immigrants elsewhere in the country has filled detention facilities above the capacity Congress set for funding. The total number of people in ICE detention has grown by more than 4,000 in the last month, to nearly 44,000.

At the same time, far fewer immigrants are being paroled or released than in the first few weeks of the Trump administration and during the Biden administration.

Under President Joseph R. Biden Jr., many people who were not considered a threat to the community or a flight risk were allowed to leave detention under certain conditions, but this practice has nearly ended. ICE stopped granting parole to detainees almost entirely in late February. A small number are still being released from detention after paying a bond or promising to meet certain conditions.

The administration has said its strategy is focused on detaining and deporting criminals, and a majority of those in detention have been convicted of a crime. But data shows the share of people detained with no criminal charges has grown to 16 percent from 6 percent in mid-January.

Some members of the administration, including Tom Homan, the ICE director, have expressed frustration that the enforcement numbers are not higher as they seek to deliver on one of Mr. Trump’s signature promises.

At the current pace, the administration does not appear on track to detain and deport millions of people this year, but the numbers could still rise quickly. Republicans in Congress have proposed billions in new funding for ICE and other agencies, and Mr. Trump has moved to expand the military’s role in immigration enforcement.