(NewsNation) — Lawmakers held a hearing Thursday where they heard testimony from people concerned that some may be coming through the border with malicious intent.

At the hearing, called “Beyond the Border: Terrorism and Homeland Security Consequences of Illegal Immigration,” Kelly Brown, a former military adviser to U.S. Customs and Border Protection, blamed a change of policy under the Biden administration leading to these issues.

“While I was serving in the (Trump) administration, there was this consolidated effort, not only with action on the ground, but most importantly, with policies at the federal level, to ensure that we take great steps to close our border and discourage folks from entering illegally,” Brown said.

Border Patrol agents conduct criminal and national security checks whenever they arrest someone. This includes cross-referencing names with a terrorist data set from the FBI. Not all of the individuals flagged on this watchlist are terrorists themselves, though. Some may just have a connection to a terrorist organization.

Some of the systems can take several days to produce red flags, however. Often by that time, individuals who were previously apprehended have already been released, sometimes with a notice to appear at a later date.

At another hearing Wednesday, a retired sector chief from San Diego, California, said he saw an uptick in what are called “special interest” migrants while President Joe Biden has been in office. Before, there were an average of 10 to 15 special interest migrants, but in 2022, there were over 100 reported, Aaron Heitke said.

“These are only the ones we caught at the time,” Heitke said. “I was told I could not release any information on this increase in (special interest migrants) or mention any of the arrests. The administration was trying to convince the public there was no threat at the border.”

Officials working for the Biden administration have maintained, however, that their actions at the border have blessed crossings. While arrest figures at the border hovered near all-time record lows in August, according to NewsNation partner The Hill, there was still a 3% jump over the previous month.

“The data published today by U.S. Customs and Border Protection shows that since President Biden announced new, decisive executive actions to secure the border on June 4, encounters between ports of entry have dropped significantly and remain at their lowest level in years,” White House spokesperson Angelo Fernández Hernández said in a statement.