U.S. authorities are reviewing a classified terror watch list of about 18,000 people after it emerged that only one of three Afghan nationals arrested in recent high-profile cases was on the list, the New York Post reported, citing an intelligence source.

According to the NY Post, the revelation has raised concerns that some suspects may have been radicalized after arriving in the United States. The issue gained renewed attention following last month’s shooting of National Guard members in Washington, DC.

National Counterterrorism Center Director Joe Kent told lawmakers at a December 11 hearing that around 18,000 known or suspected terrorists entered the U.S. over a four-year period under the previous administration. Since then, officials have been combing through the database to assess potential threats and examine how certain individuals were admitted into the country.

Jaan Shah Safi was the only one of three recently arrested Afghan nationals listed in the Terrorist Identities Datamart Environment (TIDE), the U.S. government’s central terror database. Safi, who arrived in the U.S. in 2021 under Operation Allies Welcome, is accused of providing weapons and other support to ISIS-K. U.S. officials say he remains in ICE custody pending removal proceedings.

The other two suspects — Rahmanullah Lakanwal, charged with killing a National Guard member in Washington, and Mohammad Dawood Alokozay of Texas, accused of threatening a suicide attack — were not on the watch list, according to the Post. Intelligence officials cited in the report said this suggests they may have been radicalized after entering the United States.

The Post said the Office of the Director of National Intelligence has identified nearly 2,000 Afghans with suspected terror ties and continues to share intelligence with law enforcement agencies.

The issue has reignited debate over the vetting process used during the rapid evacuation of Afghans in 2021, when more than 100,000 people were brought to the United States.

Lawmakers and officials quoted by the New York Post called for closer scrutiny of those admitted during that period, amid growing political and public concern over national security and immigration policy.