The Department of Homeland Security is actively investigating just 3,000 of the 6 million individuals who have overstayed their visas and now reside in the United States illegally, according to disclosures made before Congress.

Craig Healthy, Homeland’s assistant director for national security investigations, admitted that there are just 3,000 active investigations, or .05 percent, into some six million aliens who have illegally overstayed their visas in the United States during the past 20 years.

Investigators have additionally "exhausted" 1,626 "leads" into these individuals, Healy disclosed under questioned by Sen. David Perdue (R., Ga.), a member of the Senate Immigration Subcommittee.

Healy’s disclosure comes on the heels of a report by DHS revealing that more than half a million aliens overstayed their temporary visas in the United States in 2015 alone and ore than 482,000 of those individuals are believed to still be residing illegally in the United States, according to the report.

This includes 219 illegal overstays from Afghanistan, 681 from Iraq, 564 from Iran, 56 from Libya, 1,435 from Pakistan, 440 from Syria, and 219 from Yemen, according to the report. Many are still in the United States illegally.

Perdue questioned Healy about why the department is investigating so few of these cases.

"Roughly, we have about 3,000 that are still under investigation right now," Healy said. "1,626 leads have been what we call exhausted, meaning that we haven’t been able to locate the individual. It comes back to us, into a continuous monitoring status."

This encompasses those who have illegally overstayed their visa during the past 20 years.

"So, 3,000 [overstays] were investigated, are under investigation right now. But those 3,000 could’ve come in any one of the years in the last 20 years, correct?" Perdue asked.

"That is correct, sir," Healy said.

Perdue went on to ask how many of these individuals who overstayed their visas were reported, located, and removed from the country.

"I’ve seen estimates as high as 40 percent of the total number of illegal immigrants here, came in and overstayed a visa," Healy responded.

Perdue expressed alarm at Healy’s response and advocated in favor of a biometric detection system that can more accurately track and account for those aliens granted temporary visas.

"My question is if it’s 40 percent of whatever that top number, we have 4, 5, 6 million people here who overstay their visa. Directionally, that’s fairly correct," Perdue said. "And last year, we identified and investigated 3,000? So, you can kind of see where I’m going here. We have a monumental issue here. Even if we were to put biometric in, and have all of the 100 percent accurate information on exit, we’ve got this huge, built-up issue."

"So, am I directionally correct?" Perdue asked. "I’m not trying to draw a conclusion, but I am trying to get information."

"You’re correct, sir," Healy said.

DHS found that 527,127 aliens temporally granted U.S. business and tourist visas were found to have stayed in the United States longer than legally permitted in 2015.

Of those who did not leave the United States on time, around 482,781 are believed to still be illegally residing in the United States, according to the DHS report.

The statistics were offered as the Obama administration gears up to grant around 170,000 visas to immigrants from Muslim-majority nations in 2016.

"If Amazon and Fed Ex can track packages from a warehouse in North Carolina to a small town in rural Iowa, surely the federal government should be able to track people entering and exiting our country," said a Senate GOP aide.

"The whole purpose of a visa is to legally document people entering and leaving our country, but if the government cannot even produce this basic information, then visas have basically become a one way ticket," the aide said.