Immigration authorities said the men, detained during checks at an employee entrance gate, were Latin Americans working on construction projects at the airport in Dulles, Va., The Washington Post reported.

"There's no indication that any of the aliens were involved in any terrorist activity at all," the newspaper quoted Mark McGraw, deputy special agent in charge with the Department of Homeland Security's Immigration and Customs Enforcement agency, as saying.

McGraw said the operation began about 5 a.m., when ICE agents working in conjunction with airport and transportation authorities set up a checkpoint at one of the southern drive-through entrances.

A similar enforcement effort in June 2006 resulted in 55 arrests.

McGraw said while unusual, such inspections are important to safeguard U.S. airports.

"This is a critical, sensitive facility so ... of course we pay particular attention to it," he said. "It's one of the highest priorities of the Department of Homeland Security."

The workers were being held administratively on immigration violations while authorities determined whether criminal charges were warranted against them or their employers, McGraw said.