More than 600,000 foreign travelers who legally entered the United States in 2017 overstayed their visas and remained in the country by the end of the year, according to Department of Homeland Security data released Tuesday.

That figure represents only 1.15 percent of the more than 52 million foreigners who legally entered the U.S. through air and seaports in 2017, and is down from 1.25 percent the year before. But it marked the second straight year that more than 600,000 visitors stayed past the expiration of their visa, turning them into undocumented immigrants at risk of deportation.

President Donald Trump has urged Congress to complete a biometric entry-exit tracking system that would better monitor foreigners who legally visit the United States. Completion of that system, which uses fingerprints and iris scans to more accurately capture when people enter and exit the country, was included in an executive order he signed shortly after being sworn in as president.