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President Donald Trump said he delivered what he promised on immigration when hundreds of people were arrested in enforcement operations last week.

But Immigration and Customs Enforcement's fugitive operation teams have been carrying out such operations for years and during the eight years Obama was in office, they became more precise about picking up immigrants who were priorities for deportation.

Under Obama, those priorities were immigrants who were criminals, those who were a public safety or national security threat and those who illegally entered the country after January 1, 2014.

Whether Trump has unleashed a "deportation force" different from Obama's will come down to numbers the Department of Homeland Security didn't include in its news releases about its arrests: how many people who are not priorities as defined by the Obama administration were picked up by ICE in last week's raids and how many are being detained and deported.

The crackdown on illegal criminals is merely the keeping of my campaign promise. Gang members, drug dealers & others are being removed! — Donald J. Trump (@realDonaldTrump) February 12, 2017

In a statement, Homeland Security Secretary Richard Kelly said 75 percent of the 678 people arrested were convicted criminals. They were arrested in the areas overseen by Los Angeles, Chicago, Atlanta, San Antonio and New York.

News releases issued by DHS listed crimes for which immigrants were arrested, but did not detail how many people had no convictions or how many entered the country after the Jan. 1, 2014 date set by Obama.

The type of crime also matters. Under Obama, the priorities were those who had committed at least one felony or a misdemeanor of significance — such as drunk driving or dealing drugs — or three misdemeanors.

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According to ICE's website, 99.3 percent of ICE removals in 2016 “clearly” met the Department of Homeland Security’s priorities.

NBC News reached out to three ICE press officers by email and phone for further information on those arrested last week, but the officers responded by referring to news releases that accompanied a statement by Kelly.

Related: ICE Arrests Stir Fear In Immigrants Wary of Trump's Orders

Fugitive operations teams had been far less targeted before Obama took office.

In a 2009 analysis of the Bush administration's ICE fugitive operations teams, the Center for Migration Policy found that despite a huge increase in money from Congress - from $9 million to $218 million – and a 1,300 percent increase in personnel, the share of immigrants with criminal convictions who were arrested by the teams was decreasing.

Between 2003 and February 2008, 73 percent of individuals apprehended by fugitive operations teams were people without criminal convictions, the report said.

In the years since the 2009 report, the fugitive operations teams “have become very good at targeting" arrests according to the (Obama) administration’s priorities, said Doris Meissner, director of the Migration Policy Center’s U.S. Immigration Policy Program. She served as Immigration and Naturalization Service commissioner in the Clinton administration.

ICE said in a draft statement sent to NBC News Friday that of the 160 arrested in Los Angeles, 150 had criminal histories.

The agency said 10 people without criminal convictions were taken into custody and five had final orders of removal or had been previously deported. That information was not in the release issued Monday.

Related: ICE Says California Immigration Raids Planned Before Trump's Orders

Obama’s priority system has been a source of complaint for Republicans, groups who want severe enforcement and the head of the ICE union.

“That’s something detractors, especially (then Sen.) Jeff Sessions and the anti-immigrant groups complained bitterly about. The complaint was that Obama was more and more foregoing interior enforcement,” Meissner said. Sessions is now the U.S. attorney general.

If Trump implements his executive orders and those have become or do become the guidance for arrests, ICE may return to its less targeted approach, which means more people could be subject to deportation.

That's a possibility that many in the immigration community had been bracing for and that helped spread panic and fear during the ICE arrests made last week. That fear was heightened with the deportation of Guadalupe Garcia de Rayos, who had used a false Social Security number to get a job and was convicted of criminal impersonation. Many immigrants use false or stolen Social Security numbers to work but have not necessarily been a high priority for deportation.

Under Trump, de Rayos could be a target for fugitive operations teams.

Trump’s orders allow for arrest and removal of those convicted of a crime or charged with one, as well as those immigrants that authorities suspect have “committed a chargeable criminal offense.” The latter could be illegal entry, driving without a license or using a fake Social Security number.

His executive order also prioritizes for removal people who have "engaged in fraud or willful misrepresentation" before a government body, abused a public benefits program, have a final order of removal or in the judgment of an immigration officer pose a risk to public safety or national security. His orders have called for the removal of people found to have immigration violations once their removal proceedings are complete.

In future sweeps, how many people are arrested who are criminals will be key to knowing whether Trump is unleashing a deportation force. Trump has stated criminals are his focus, but his executive orders "go far broader than that," Meissner said.

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