Secretary of Homeland Security Jeh Johnson speaks during a news conference in Newark, N.J., Aug. 11, 2015. (Eduardo Munoz/Reuters)

The Department of Homeland Security’s use of a controversial tool to deport illegal immigrants fell 30 percent in recent months, continuing a longer-term decline dating back several years, a new report says.

U.S. Immigration and Customs Enforcement in April lodged 30 percent fewer requests with local police departments to hold immigrants targeted for deportation than the agency had in October, according to the Transactional Records Access Clearinghouse (TRAC), an independent research organization at Syracuse University.

The requests, known as detainers, have come under fire from police and immigrant advocates, and a series of federal court decisions have raised legal and constitutional questions about them. The requests ask police to hold immigrants ICE wants to deport for up to 48 hours after their scheduled release from custody.

The report is an early indicator that a profound shift in the nation’s enforcement of immigration laws, begun by DHS Secretary Jeh Johnson, may be on track toward working as planned. Johnson in November took steps to ensure that the majority of the United States’s 11.3 million undocumented immigrants can stay in this country, instructing agents to narrow enforcement efforts to three groups of illegal migrants: convicted criminals, terrorism threats or those who recently crossed the border.

(Obama administration scales back deportations in policy shift)

A key part of the shift was Johnson’s elimination of a program known as Secure Communities, a George W. Bush administration initiative that was initially expanded under President Obama. It used the much-criticized detainers to scoop up some long-term illegal immigrants with families and community ties who were arrested for minor offenses and then deported.

DHS has replaced Secure Communities with a new Priority Enforcement Program. Under that program, ICE will still coordinate with police to deport illegal immigrants, but will limit its use of detainers. Instead, officials say, ICE will emphasize less controversial notification requests, under which ICE will ask to be notified 48 hours before an immigrant is released from custody.

(New DHS Deportation Program meets with resistance)

While detainer usage has dropped significantly since Johnson’s directive about the changes in November, ICE’s use of detainers had actually been decreasing for several years, the report says. Detainer use peaked in March 2011, when nearly 28,000 were issued, it said. That compares with only 7,993 detainers issued in April.

“The decline in the use of detainers does parallel a period of growing criticism of the Secure Communities program by state and local law enforcement agencies, immigration rights groups, and others,” the report said.

Jennifer Elzea, an ICE spokeswoman, said the agency determines detention requests for immigrants “on a case-by case basis with a priority for detention of serious criminal offenders and other individuals who pose a significant threat to public safety.”

She added that ICE  “is focused on smart, effective immigration enforcement that prioritizes the removal of criminal aliens, recent border crossers and egregious immigration law violators, such as those who have been previously removed from the United States.”

A DHS official, speaking on condition of anonymity to discuss internal numbers and policies, said the department “cannot verify how TRAC pulled their data for this particular report.” TRAC said the report was based on data obtained directly from ICE through requests filed under the Freedom of Information Act.