The Obama administration on Monday announced enhancements to the Visa Waiver Program amid growing concern about the threat of foreign fighters linked to the Islamic State of Iraq and Syria.

“Effective today, those seeking to travel to the United States from countries in our Visa Waiver Program will be required to provide additional data fields of information in the travel application submitted via the electronic system for travel authorization,” said Department of Homeland Security Secretary Jeh Johnson. “The new information sought includes additional passport data, contact information and other potential names or aliases.”

Under the Visa Waiver Program, travelers from certain countries can enter the U.S. for up to 90 days without having to obtain a visa.

The heightened measures also come after the administration stepped up security at federal government buildings in the wake of the deadly shooting near Canada’s Parliament building.

U.S. officials have increasingly said that foreign fighters pose a major threat to the homeland, especially if their travels go undetected.

“We are taking this step to enhance the security of the Visa Waiver Program,” Johnson explained, “to learn more about travelers from countries from whom we do not require a visa.”