Arrests and deportations by U.S. Immigration and Customs Enforcement (ICE) plummeted in fiscal year 2021 as the agency entered a “new era” under the Biden administration, which directed officers to focus on detaining immigrants with serious criminal convictions, government figures released Friday show.

ICE deportation officers arrested 74,082 immigrants in fiscal year 2021, which ended in October, a 28% drop from 2020, when arrests also decreased sharply because of the start of the coronavirus pandemic.

The agency carried out 59,011 deportations in fiscal year 2021, an all-time low, according to historical ICE data. The previous low came in fiscal year 2004, when ICE recorded 175,106 deportations.

The sharp decrease in ICE arrests and deportations is largely a reflection of the Biden administration’s efforts to reshape the agency’s work and narrow the groups of immigrants whom agents should detain. Administration officials also cited a “complex environment” during the pandemic that played a role in limiting arrests and deportations.

Current rules instruct ICE officers to detain immigrants convicted of serious crimes, migrants who recently crossed a U.S. border illegally, and those deemed to pose a national security risk, such as suspected terrorists. Under the Biden-era rules, officers generally refrain from arresting immigrants with clean records if they have lived in the U.S. for years.

The Biden administration has generally barred ICE officers from detaining victims of serious crimes and pregnant or nursing women, and discontinued worksite sweeps and the long-term detention of migrant families with children. ICE officials also tried to implement a 100-day deportation moratorium during President Biden’s first week in office, but that plan was blocked by a Texas lawsuit.

Republicans have strongly opposed the policy changes at ICE, accusing the administration of not fully enforcing immigration laws at a time when border arrivals have soared. Progressives have also expressed frustration, criticizing officials for not further curtailing ICE detention and arrests.

During a call with reporters Friday, a senior ICE official who requested anonymity defended the administration’s policies, saying “fiscal year 2021 ushered in a new era at ICE.” The agency, the official argued, is using finite enforcement resources to detain immigrants who could pose a risk to public safety.

“We are focusing on what we consider quality arrests, sort of the ones that are the most severe threats to our communities,” another senior ICE official said during the call.

ICE arrests of immigrants convicted of “aggravated felonies” rose to 12,025 in 2021, up from 6,815 in 2020. Under U.S. immigration law, “aggravated felonies” are a range of crimes that include serious, violent offenses like murder and rape, as well as other crimes that are deemed misdemeanors in some states.

Collectively, immigrants arrested by ICE in fiscal year 2021 had been convicted of a combined 1,506 homicide-related offenses, 3,415 sexual assaults, 19,549 assaults, 2,717 robberies and 1,063 kidnappings, the agency said in a report published on Friday.

ICE also highlighted a slight increase in “at large” arrests, which occur during targeted operations in communities, as opposed to transfers from state or federal criminal custody. ICE recorded 25,993 at-large arrests in 2021, compared to 23,932 in 2020.

Nearly 500 of those arrests occurred during an operation last year targeting sex offenders, 80% of whom had been convicted of crimes involving the victimization of children, the ICE report noted.

Sixty-six percent of the 59,000 immigrants deported this past fiscal year had criminal records, an increase from 56% in 2020, ICE said. The rest were primarily migrants transferred from border custody. The agency said it also deported 2,718 alleged gang members and 34 suspected terrorists.

The deportation tally does not include 36,654 air expulsions that ICE said it carried out on behalf of U.S. border officials to expel migrants processed under a Trump-era pandemic restriction known as Title 42.

The Biden administration has also pledged to reform the ICE detention system, which mainly consists of a network of dozens of country jails and for-profit prisons with agency contracts.

The agency stopped detaining immigrants at two facilities plagued by allegations of detainee mistreatment last year but has yet to take public steps to fulfill Mr. Biden’s campaign promise to end for-profit immigration detention.

ICE has expanded so-called “alternatives to detention” programs under Mr. Biden. The programs allow the agency to track migrants in deportation proceedings, through ankle monitors, other GPS devices and home curfews, without physically holding them in a detention center.

More than 182,000 immigrants were enrolled in alternative to detention programs as of late last month, according to ICE data. The agency was also holding another 18,000 immigrants in detention facilities.