A new government report released Tuesday night found more than half a million foreign nationals who received temporary visas to enter the U.S. under the Visa Waiver Program or B Visa in 2015 overstayed their permits.

A total of 527,127 people visiting the U.S. through both programs failed to leave and have remained in the country without legal status or lawful presence. According to the report, more than 90 percent of those who remained in the country illegally, a total of 482,781, were believed to still be present through the end of last year, according to Department of Homeland Security data.

"These figures reveal the disintegration of our immigration system before our very eyes," a GOP Senate aide told the Washington Examiner. The aide noted that that the report does not include figures from other major visa programs, including the F-1 student visa, multiple H and L foreign worker visas, and the J-1 exchange visa.

DHS cast the report as good news, given that nearly 45 million people used the visas in question, making the "overstay rate" just 1.17 percent.

"In other words, 98.83 percent had left the United States on time and abided by the terms of their admission," DHS said.

But a number of countries with ties to terrorism had significant numbers of nationals still in the U.S. accounted for by the federal government: 1,435 from Pakistan, 681 from Iraq, 564 from Iran, 440 from Syria, 219 from Yemen, 219 from Afghanistan, and 56 from Libya.

The new information was released hours before the Senate Subcommittee on Immigration and the National Interest is set to question multiple Homeland Security officials about the federal agency's refusal to set up a statutorily required biometric entry-exit system.

Chairman Jeff Sessions, R-Ala., is expected to question the witnesses on why the Obama administration has not enforced immigration laws by removing visa overstayers or implemented the tracking system.