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Republican lawmakers are voicing concern about the "potential risks" of a Department of Homeland Security decision granting "trusted traveler" status to airline passengers from Saudi Arabia.

Rep. Michael McCaul, R-Texas, chairman of the House Homeland Security Committee, and six other lawmakers questioned the program in a letter Wednesday to Homeland Security Secretary Janet Napolitano.

They asked for "assurances" about whether Saudi applicants would receive proper screening before being enrolled and what steps would be taken to prevent terrorists from exploiting the system. They noted, as other critics of the decision have, that Saudi Arabia produced 15 of the 19 hijackers behind the Sept. 11, 2001, terrorist attacks.

"Certainly, despite our longstanding relationship with the Kingdom, there are potential risks in opening this program to Saudi Arabia that must be considered," they wrote.

They noted that Saudi Arabia also was temporarily on a list of countries whose U.S.-bound travelers would face higher scrutiny following the attempted Christmas Day bombing in 2009.

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The Investigative Project on Terrorism issued a report last week on the department's under-the-radar announcement to expand the Global Entry program to Saudi Arabia -- which was first made by Napolitano after meeting in January with her Saudi counterpart. Any Saudi travelers cleared through the program will be able to bypass the normal customs line after providing passports and fingerprints. The status lasts for five years. Applicants are expected to undergo a thorough vetting before they are accepted.

Only an exclusive handful of countries enjoy inclusion in the Global Entry program -- Canada, Mexico, South Korea and the Netherlands. According to the IPT, some officials were questioning why Saudi Arabia gets to reap the benefits of the program, when key U.S. allies like Germany and France are not enrolled.

The lawmakers who wrote to Napolitano said they remain "vigilant for vulnerabilities that our enemies can exploit" to get inside U.S. borders.

"Expanding Global Entry to high-risk countries may represent such a risk," they wrote.