More than 13,000 immigrants convicted of homicide — either in the United States or abroad — are living outside of Immigration and Customs Enforcement detention, according to data ICE provided to Congress earlier this week.

The immigrants are part of ICE’s “non-detained” docket, meaning the agency has some information on the immigrants and they have pending immigration cases in the U.S., but they are not currently in detention either because they are not prioritized for detention, they are serving time in a jail or prison for their crimes, or because ICE cannot find them, three law enforcement officials said.

Two of the officials said it is not known how many are incarcerated because ICE is not always privy to that data from state and local law enforcement agencies.

Acting ICE Director P.J. Lechleitner sent the data, collected as of July 21, as part of a request sent in March from Republican Rep. Tony Gonzales of Texas.

A spokesman for the Department of Homeland Security said the data sent to Gonzales is being misinterpreted, and goes back four decades, long before the Biden administration.

It is not clear when the first migrant of the 13,000 crossed into the U.S. Two law enforcement officials familiar with the data told NBC News many of the migrants on ICE’s non-detained docket, including serious criminals, crossed into the U.S. under previous administrations, including that of former President Donald Trump.

A high number of non-detained immigrants with criminal convictions is not new, though it has grown in recent years.

A 2016 DHS Inspector General's report found there were 368,000 criminal immigrants who were not detained by ICE. According to ICE's fiscal year 2023 budget justification, there were 405,786 convicted criminal immigrants on the non-detained docket as of June 5, 2021, just under five months after Trump left office, indicating many crossed during the Trump administration. As of July of this year, according to the data provided by ICE to Rep. Gonzales, over 435,719 convicted criminal immigrants were on ICE's non-detained docket.

A DHS spokesman told NBC News in a statement: "The data in this letter is being misinterpreted. The data goes back decades; it includes people who entered the country over the past 40 year or more, the vast majority of whose custody determination was made long before this administration. It also includes many who are under the jurisdiction or currently incarcerated by federal, state or local law enforcement partners."

During a campaign stop in Michigan on Friday, Trump used the data to criticize Vice President Kamala Harris for current immigration policies.

“I can finally look at them and say ‘I told you so’ to the fake news,” Trump said. “These are hard, tough, vicious criminals that are free to roam in our country.”

The White House has yet to comment on the data. One official told NBC News the release of the data came as a surprise to the White House.

The 13,099 immigrants convicted of homicide living in the U.S. may have never had contact with ICE, the two law enforcement officials said. Some may have crossed the border and then been released because Border Patrol lacks information on their criminal history. In many cases, the U.S. is not notified of someone’s criminal conviction until after they cross into the country.

In other cases, migrants convicted of crimes may be released by state and local officials after they serve their time without ICE being notified, as is policy in many sanctuary cities. ICE then has to locate the person after release in order to detain and deport them.

The two law enforcement officials said ICE prioritizes migrants who have been convicted of serious crimes, like homicide, for arrest.

But the agency’s limited resources limit how many they can locate and arrest. There are currently more than 7.5 million immigrants on ICE’s “non-detained” docket, meaning they have pending immigration cases but are not currently in detention.

Lechleitner told NBC News more local jurisdictions are cooperating and starting to rethink their sanctuary policies in light of increased attention on crimes committed by migrants.

NBC News joined ICE agents in Maryland earlier this year when they arrested a man convicted of murder in Colombia and a man convicted of attempted murder in El Salvador.

Agents explained that locating convicted criminals living at large takes an enormous amount of manpower, from locating them to the arrest.