Immigration and Customs Enforcement recently arrested an Uzbek man in Baltimore with alleged ISIS ties after he had been living inside the United States for over two years, according to two U.S. officials.

The man, 33-year-old Jovokhir Attoev, crossed the border into Arizona and was apprehended by Border Patrol in February 2022, the officials said. At the time, neither Customs and Border Protection nor ICE could find any derogatory information on Attoev. He was released inside the U.S. on bond.

Then, in May 2023, Uzbekistan put out an international notice that Attoev was wanted in his home country for his alleged affiliation with ISIS.

For more on this story, tune in to NBC Nightly News with Lester Holt tonight at 6:30 p.m. ET/5:30 p.m. CT or check your local listings.

But it was not until March 2024, almost a year later, when the U.S. government was reviewing Attoev’s application for asylum, that officials discovered the notice from Uzbekistan and connected it with the man living in Maryland.

After the connection was made, ICE arrested him on April 17 in Baltimore. Attoev is currently in custody in Pennsylvania, according to the ICE website. He’s awaiting trial in immigration court next week in New Jersey, where ICE lawyers will likely argue that they need to keep him detained in order to glean more information about his potential ties to ISIS.

Multiple former Department of Homeland Security officials interviewed by NBC News said the case raises concerns about how quickly and frequently the U.S. can do follow-up vetting on migrants who have already crossed the border.

While no derogatory information existed on Attoev at the time he crossed the border in 2022, the notice from the Uzbek government in 2023 was not initially checked against the list of immigrants living in the U.S. and awaiting court hearings.

Elizabeth Neumann, who served as assistant secretary for counterterrorism and threat prevention at DHS from 2017 to 2020, said Congress should pass the bipartisan border security legislation that was blocked by Republicans earlier this year and allocate more money for counterterrorism.

“The concern I have is that in the last decade or so our counterterrorism budgets have drastically decreased,” Neumann said. “And that means we have [fewer] analysts doing this work. So it is harder to do things in a really timely manner when you have [fewer] resources.”

She added that counterterrorism budgets decreased after the destruction of the ISIS caliphate in the Middle East. But since then, particularly because of the fall of the Afghan government in 2021, ISIS has reemerged as a threat. A branch of ISIS, Islamic State Khorasan (ISIS-K), claimed responsibility for a deadly gun attack in Moscow in March. 

In February, Director of National Intelligence Avril Haines told a Senate hearing that ISIS “remains a significant counterterrorism concern for us.” 

There is no indication that ISIS has managed to organize a secret network inside the United States, and if a militant managed to cross over the U.S. border, they would be hard-pressed to organize an attack without such a network, according to Colin Clarke, a senior fellow at the Soufan Center, a nonprofit center focused on global security issues.

Multiple law enforcement officials told NBC News that the U.S. has not definitively determined whether Attoev is a part of ISIS or if he ever carried out or planned to carry out an attack. DHS continues to seek information and is questioning him further while he is in detention, the officials said. 

In a statement, a DHS spokesperson said, “DHS screens and vets individuals seeking to enter the United States to identify national security or public safety threats and takes appropriate action, to include preventing an individual from entering the country. Screening and vetting evaluates information available to the U.S. Government at that time. If individuals who have entered the country are later found to be associated with information indicating a potential national security or public safety concern, DHS and our federal partners investigate and we detain, remove, or refer them to other federal agencies for further vetting and prosecution as appropriate. In this case, the individual is in U.S. custody and there is no threat to public safety.”

NBC News previously reported that another migrant, an Afghan named Mohammad Kharwin, 48, was on the U.S. terror watchlist but was released by CBP because they did not have enough information to connect him to the watchlist at the time he crossed. He spent nearly a year inside the U.S. before he was arrested in San Antonio. He was released again on bond after a court hearing and then arrested again hours after NBC News published a story on his case.

The national terrorist watchlist, which is maintained by the FBI, includes the names of 1.8 million people considered potential security risks. The database indicates Kharwin is a member of Hezb-e-Islami, or HIG, a political and paramilitary organization that the U.S. has designated a terrorist organization.

Attoev was not on the watchlist at the time he crossed the border in 2022 or at the time he was arrested in April, according to the U.S. officials.

The percentage of migrants with terror ties crossing the border remains extremely low. An NBC News analysis found that the percentage of migrants on the terrorist watchlist as a proportion of the total number of CBP encounters across U.S. borders was slightly lower during the Biden administration than during the Trump administration. It has averaged 0.02% during the Biden administration, lower than the 0.05% it averaged under Trump.

In fiscal year 2023, which ended in late September and saw a surge in border crossings, CBP had 736 encounters with migrants on the terrorist watchlist at U.S. borders, the most in the past six years. The second highest year was 2019, during the Trump administration, when CBP had 541 encounters with migrants on the watchlist.

It is not known whether any migrants on the watchlist or who were named in international notices as having suspected terror ties were released into the U.S. during the Trump administration.