GTON: In this June 5, 2015 file photo, a view of the Homeland Security Department headquarters.—AP

SAN DIEGO: Nearly 740,000 foreigners who were supposed to leave the United States during a recent 12-month period overstayed their visas, the Homeland Security Department said Monday, detailing a crucial but often overlooked contributor to the number of people in the country illegally. President Donald Trump has proposed spending billions of dollars to erect a wall on the US border with Mexico and hire more border agents, but those measures would not address people who arrive legally and stay after their visas expire.

An estimated 40 percent of the roughly 11 million people in the country illegally stayed past their visas. There were 739,478 overstays from October 2015 through September 2016 among visitors who arrive by plane or ship - more than the population of Alaska. The total number of overstays is much larger but has not been quantified because the statistic doesn't include how many people leave by land. The cost and technological hurdles to develop a checkout system at congested land crossings are enormous because the sites are so busy.

Last year, Homeland Security tested facial scans at a San Diego border crossing but has npt said if the technology works or will be expanded. Homeland Security last year published the number of overstays for the first time in at least two decades, saying 527,127 people who came by air or ship stayed past their visas from October 2014 to September 2015. This year's report added student and foreign exchange visitors and many visa categories for temporary workers, while last year's only counted business travelers and tourists.

Homeland Security said it will make additional improvements in future reports, including more data on people who cross by land. Overstays accounted for 1.5 percent of the 50.4 million visitors who arrived by plane or ship in the latest period, Homeland Security said. Canada occupied the top slot for overstays among business travelers and tourists, followed by Mexico, Brazil, Venezuela and the United Kingdom. Germany, Colombia, China, India and Italy rounded out the top 10.

The overstay rate was much higher among students and foreign exchange visitors, with 79,818 of 1.5 million, or 5.5 percent, staying after their visas expired. China had the largest number of student overstays, followed by Saudi Arabia, South Korea, India and Brazil. Trump vowed during last year's campaign to finish building a system to record when visitors leave the country by using biometric identifiers, like facial or iris scans, but he has focused much of his attention on building a wall and hiring more border agents.

Homeland Security's internal watchdog said earlier this month that immigration agents waste their time logging in and out of archaic computer systems while trying to track down foreigners suspected of overstaying their visas only to find out later that many visa holders have left the country.--AP