WASHINGTON (Reuters) - U.S. immigration officials said on Wednesday they had arrested 55 illegal immigrants who were working at a construction site in the secure area at Dulles International Airport.

Agents from Immigration and Customs Enforcement made the arrests early in the morning as the workers were being bussed to the construction site and were attempting to pass through a security checkpoint.

ICE said in a statement that one of the workers had a security badge that grants unescorted access to the tarmac of the Virginia-based airport that serves Washington DC.

"Unauthorized workers employed at sensitive sites and critical infrastructure facilities ... pose serious homeland security threats," said Julie Myers, assistant secretary of homeland security in charge of ICE.

"Not only are the identities of these individuals in question but these aliens are also vulnerable to exploitation by terrorists and other criminals given their illegal status in this country," she added in the statement.