Tens of thousands of illegal immigrants previously convicted of crimes in the U.S. have been apprehended trying to enter the country via the Southwest border over the past 2.5 years, according to U.S. Customs and Border Protection data provided to Breitbart News.

Since fiscal year 2014, CBP agents have apprehended nearly 47,000 criminal aliens — over 6,400 of whom were caught more than once — illegally crossing the U.S.-Mexico border.

Specifically, CBP agents apprehended 21,887 criminal aliens, including 3,416 criminal alien recidivists in FY 2014. In FY 2015 there were 18,645 criminal alien apprehensions and 2,366 criminal alien recidivists, and in FY 2016 through April 12 there have been 6,435 criminal alien apprehensions and 626 criminal alien recidivists.

The numbers, as some experts pointed out, appear lower than expected — especially when viewed against Immigration and Customs Enforcement’s removals of aliens apprehended at the border. In FY 2015, for example, ICE removed 235,413 aliens, 165,935 of whom were removed due to an apprehension at or near the border. Of those 165,935 border apprehension removals, 75,829 were criminals.

CBP stressed, however, that it does not have jurisdiction over those aliens who commit crimes after entering the U.S. and that the new CBP numbers are specifically illegal immigrants who already had a criminal record in the U.S. and were apprehended at the Southwest border.

“U.S. Customs and Border Protection’s agents and officers protect America by preventing terrorists and criminals from entering the country while welcoming legitimate travelers and commerce,” CBP spokesman Dan Hetlage said in a statement to Breitbart. “Our highly trained law enforcement personnel apprehend more than 1,000 individuals each day for suspected violations of U.S. Laws.”

Jessica Vaughan, the director of policy studies at the Center for Immigration Studies, on the other hand, suggested that the low criminal alien apprehensions at the border could be indicative of weaknesses in the system.

“Since the Border Patrol still lacks the situational awareness and capability to know how many are undetected, and much of the border is not secured, and the Border Patrol has been forced to stand down rather than patrol aggressively, the decline in criminal alien apprehensions may be cause for concern, not confidence,” she wrote in an email to Breitbart News.

And the numbers of criminal aliens apprehended at the Southwest border is likely a fraction compared to the criminals who make it across, according to testimony National Border Patrol Council President Brandon Judd offered before a House panel in February.

“A safe estimate from the Border Patrol agents would be that we arrest about 40 percent of what actually crosses,” Judd told the House Judiciary Subcommittee on Immigration and Border Security.

“So if you’ve got the official numbers from the agency about what we actually arrest, that’s about 40 percent of what comes,” Judd added at the time.

Regardless, as Vaughan noted, “The fact that thousands of criminals are even attempting to cross illegally every year is cause for concern and confirms how important it is for public safety of the entire country that the federal government remain vigilant at the border. And it helps explain why states like Texas and Arizona think it is necessary to devote state resources to the problem.”