A new report from the Department of Homeland Security (DHS) states that visa overstays more than doubled in the last fiscal year, surpassing 600,000 total.

The report reveals a major portion of illegal aliens living in the U.S. are people who have stayed in the U.S. past their formal departure dates. This, combined with previous reports of technology issues faced by U.S. Immigration and Customs Enforcement (ICE) officials, presents a daunting challenge for those trying to enforce immigration laws.

During the most recent year, Fiscal Year 2016 which ended on September 30, 2016, 628,799 overstayed their visas and became illegal aliens. This compares to the Fiscal Year 2015 total of 304,000, as reported by Breitbart News.

“To protect the American people from those who seek to do us harm, and to ensure the integrity of the immigration system, ICE has recently increased overstay enforcement operations,” DHS officials stated in the report obtained by Breitbart Texas. “Each year, ICE’s Homeland Security Investigations special agents systematically review approximately one million records of individuals who violate the terms of their visas or the visa waiver program, prioritizing leads that pose national security or public safety threats.”

However, ICE special agents face challenges of outdated technology and non-connected databases as they attempt to enforce our country’s immigration laws and track down visa overstays. A DHS report from the Office of Inspector General (OIG) published earlier this month shows that ICE investigators are given a sluggishly-encumbering system, causing delays in determining whether a visa holder poses a national security threat.

The DHS OIG inspector found that:

The myriad of information systems and databases used in DHS for visa tracking were not effective in identifying nonimmigrant overstays. Some of these systems and databases were ‘stove-piped’ and did not electronically share information, resulting in numerous inefficiencies. Despite some recent system integration efforts, ICE personnel conducted cumbersome and manual searches across multiple systems for information on in-country overstays. ICE personnel periodically were unsure of which system to use and were hampered by multiple passwords required to maintain system access. Obtaining visa and immigration status on suspected overstays also was difficult due to the unstructured manner in which data were stored.

During an interview on Breitbart News Daily, Senator Rand Paul (R-KY) spoke about visa overstays: “about 40 percent of people who come to visit our country on a visa overstay their visa, and we have no idea where they are.”

The junior senator from Kentucky added, “On 9/11, at least two of the hijackers were here on visa. They were traveling back and forth to the Middle East, and we really had no idea where they were or what they were doing, and they were overstaying their visa. So, there are problems I think in the immigration system that need to be fixed for our safety.”

The increases noted in this year’s report come partially from the addition of student visas, worker classifications, and other classes of admissions, officials stated. The new report now covers 96.02 percent of all air and sea non-immigrant admissions into the U.S. during FY 2016.

“It is important to note that determining lawful status is more complicated than solely matching entry and exit data,” DHS Secretary John Kelly stated in the report. “For example, a person may receive from CBP a six-month admission upon entry, and then he or she may subsequently receive from U.S. Citizenship and Immigration Services (USCIS) a six-month extension. Identifying extensions, changes, or adjustments of status is necessary to determine whether a person is truly an overstay.”

The largest cohort of people staying past their scheduled departure dates are students. Of the 1.45 million scheduled to complete their program and depart the country, 2.5 percent stayed behind. This represents more than 37,000 students who became illegal aliens by not leaving as planned. Of these, Chinese students made up the largest number of overstays at 7,500.

Canadians had a visa overstay rate of 1.44 percent, representing 119,418 in-country overstays. Mexico accounted for 46,658 visa overstays (1.72 percent).

“During the past two years, DHS has made significant progress in terms of the ability to accurately report data on overstays—progress that was made possible by congressional realignment of Department resources in order to better centralize the overall mission in identifying overstays, DHS officials concluded. “During FY 2016, through new biometric exit tests and the BE-Mobile law enforcement tool, DHS was able to biometrically verify the biographic departure data for a limited number of departures from the United States in the air, land, and sea environments. While these only account for a very small percentage of all the biographic departure records for that FY, it is an important first step towards implementing a comprehensive biometric entry and exit system.”

Bob Price serves as associate editor and senior political news contributor for Breitbart Texas. He is a founding member of the Breitbart Texas team. Follow him on Twitter @BobPriceBBTX and Facebook.

DHS REPORT: Entry and Exit Overstay Report, Fiscal Year 2016