WASHINGTON – Concerned that Europeans who joined Islamic militants in Iraq and Syria might try to launch terrorist attacks in the West, Homeland Security officials boosted screening Monday of people traveling to the U.S. on Western passports.

Officials will seek "to learn more about travelers from countries from whom we do not require a visa," Homeland Security Secretary Jeh Johnson said in a statement.

Intelligence officials say more than 3,000 Europeans have traveled to Syria and Iraq to fight alongside the Islamic State in Iraq and the Levant (ISIL) and other militant groups since 2011.

U.S. officials are especially concerned because many of the fighters come from England, Belgium, France and Germany, and thus can travel easily.

Citizens of so-called visa-waiver countries do not need to apply overseas for a visa to enter the U.S., a process that normally entails checking international terrorism databases. The travelers instead complete an online information form at least 72 hours before departing.

That information form, called the Electronic System for Travel Authorization, was expanded on Monday.

In addition to full name, passport number and travel plans, passengers are now required to list the names of their parents, city of birth, contact and employer information, national identification number, aliases and any other types of citizenship they hold.

The additional information could help officials screen travelers against details in terrorism databases.

The change is the latest precaution the U.S. has taken as ISIL militants and other terrorist groups have expanded havens in Iraq and Syria, beheaded two American journalists and issued threats to attack American targets.

In July, the U.S. asked about 25 airports overseas to enhance aviation security after intelligence suggested an Al-Qaida affiliate in Syria had developed a new way to hide explosives in laptops and cellphones.