The Pew Research Center released an analysis of Justice Department numbers Monday showing a massive increase in the prominence of immigration-related offenses in federal law enforcement.

Pew cited a report released last month by the Bureau of Justice Statistics to show that immigration offenses accounted for fully half of federal arrests in 2014, up from only 28% a decade earlier. Consequently, the Department of Homeland Security, which includes Customs and Border Protection and Immigration and Customs Enforcement (ICE), now makes more arrests than the FBI, DEA, BATFE, U.S. Marshal’s Service, and all other branches of the Justice Department combined.

According to Pew:

The geographic distribution of federal arrests also shows the growing emphasis on immigration offenses. In 2014, 61% of all federal arrests – or more than 100,000 – occurred in just five federal judicial districts along the U.S.-Mexico border.

Driven by this massive increase in immigration arrests, a staggering 61% of federal arrests are now of non-U.S. citizens. These arrests, mostly for immigration offenses, but including thousands for other crimes, do not include the hundreds of thousands of non-criminal apprehensions of illegal aliens each year.

Illegal aliens made up an equally shocking 37% of all criminal defendants in federal district courts in 2014.

Most illegal aliens arrested for immigration offenses are referred to administrative hearings before immigration courts. The increase in this type of arrests has placed tremendous strain on that system. The resulting backlog raises concerns of a “virtual amnesty” from the inability to process these cases.

The BJS report shows that, increasingly, immigration offenses, which can include more serious crimes like trafficking aliens into the United States, are winding up in regular U.S. district courts. While, in 1994, fewer than 2,500 immigration cases wound up in district court, 21,789 did in 2014, representing over a quarter of those general courts’ criminal caseload. Of those defendants, almost 80% were sentenced to time in federal prison with a median sentence of 15 months.

The influx of illegal alien offenders and especially of immigration arrestees remains a pressure point on the federal prison system that, due to a drop in other types of offenders and changes in federal sentencing policy, has otherwise seen a drop in overcrowding. The problem is particularly acute for prisons run by private companies, which are disproportionately set aside for immigration offenders.

ICE is forced to make use of dozens of private facilities to house detainees awaiting deportation. Attorney General Jeff Sessions recently announced he would be reversing the Obama administration’s plans to phase out private prisons for criminal convicts and pre-trial detainees.

Pew notes that, by their estimates, federal arrests make up only a little more than one percent of the total arrests in the United States each year, local and state law enforcement being responsible for the vast majority of arrests.

While the numbers in the BJS report accurately reflect the federal criminal justice system, wider estimates of the proportions of crime committed by illegal aliens are hard to come by. Reporting across the nation’s hundreds of law enforcement agencies is inconsistent and incomplete. So-called “sanctuary” jurisdictions also refuse to report on their arrestees’ immigration status as a matter of policy, hindering federal efforts to collect statistics and enforce immigration laws.