The findings were revealed as Congress debates an immigration bill, and the Government Accountability Office’s report could throw up another hurdle because lawmakers in the House and Senate have said that any final deal must include a workable system to track entries and exits and cut down on so-called visa overstays.

The government does track arrivals, but is years overdue in setting up a system to track departures — a goal set in a 1996 immigration law and reaffirmed in 2004, but which has eluded Republican and Democratic administrations.

“DHS has not yet fulfilled the 2004 statutory requirement to implement a biometric exit capability, but has planning efforts under way to report to Congress in time for the fiscal year 2016 budget cycle on the costs and benefits of such a capability at airports and seaports,” GAO investigators wrote.