WASHINGTON — Arrests of noncitizens by the U.S. government more than tripled over the past decade and now account for 64 percent of all federal arrests, the Justice Department said Thursday.

"While noncitizens make up seven percent of the U.S. population, they accounted for 15 percent of all federal arrests" in 2018, according to the Bureau of Justice Statistics, which said noncitizens accounted for roughly one-quarter of all federal drug and property crime arrests.

Concern about crime committed by undocumented immigrants has been a key point in the Trump administration's push for stricter border controls. But the report showed that most of the arrests of noncitizens were for immigration offenses, not violent crimes.

Prosecutions for violating immigration laws have flooded the nation's federal courts, especially in border states. Nationwide, arrests of noncitizens for immigration offenses rose 440 percent in the two decades from 1998 to 2018 — from 19,556 a year to 105,748. By contrast, the number of noncitizens arrested for other crimes rose about 8 percent.

Compared to 20 years ago, 95 percent of the increase in total federal arrests was due to immigration offenses.

In 2018, U.S. citizens still accounted for the vast majority of non-immigration arrests — 91 percent for violent crimes, 93 percent for public order violations and 96 percent of all arrests on weapons charges.

The shift in the pattern of immigration at the southern border was reflected in the arrest figures. Central Americans accounted for less than four percent of all immigration arrests in 1998, and by 2018 that figure rose to 34 percent. Most of those arrested in the federal system for immigration violations during the 10-year period were from Mexico — 83 percent in 1998 and 60 percent in 2018.

A group that provides legal help to immigrants said the report gives a misleading impression.

"The fact that so many Central Americans fleeing violence are making their way into the crime statistics is disingenuous. It’s overlooking that they’re crossing the border to request asylum and to lump them in with criminals doesn’t give an accurate portrait of what’s going on,” said Walter Ewing of the American Immigration Council.

For decades, a debate has raged over the amount and type of crime committed by undocumented immigrants. In June, President Donald Trump tweeted that Democrats "don’t care about crime and want illegal immigrants, no matter how bad they may be, to pour into and infest our country."

But a study released in March by the libertarian Cato Institute found that incarceration rates for illegal immigrants were around half of those for native-born Americans. In Texas, Cato said, "illegal immigrant conviction rates for homicide, larceny, and sex crimes are also below those of native-born Americans." The criminal conviction rates for legal immigrants were lowest of all, its study said.

Justice Department officials say the Central American gang known as MS-13 is notoriously violent. However, the government estimates MS-13 has about 10,000 members in the United States, which is about the same as a decade ago.