ISIS may be manufacturing fake Syrian passports that it can use to smuggle its fighters into foreign countries. U.S. security officials are now warning that the group may have captured at least one machine that makes official Syrian passports and could be using it to manufacture forgeries that would make it easier for a militant to sneak undetected into a foreign country.

Both the printing machine and boxes of blank Syrian passports fell into the hands of the terrorist group last summer when it entered Deir ez-Zour, a city currently listed as ‘contested’ by the Defense Department’s map of the war-torn country.

FBI Director James Comey publicly revealed the threat in testimony on Capitol Hill regarding the release of a 17-page Homeland Security Investigations (HSI) Intelligence Report that detailed the implications of such an acquisition by ISIS.

“Since more than 17 months [have] passed since Raqqa and Deir ez-Zour fell to ISIS, it is possible that individuals from Syria with passports ‘issued’ in these ISIS controlled cities or who had passport blanks, may have traveled to the U.S.,” the report reads, according to ABC News.

The deadly seriousness of fake Syrian passports became clear in the days after the attacks on Paris when two of the suicide bombers were found to have used them to enter Europe. At least one other forged passport has been linked to ISIS-controlled territory.

Security officials report that this fake Syrian passport was manufactured in ISIS-controlled territory this year.

Despite the risk of an ISIS-fighter entering the United States with a forged passport, it’s not quite as easy hopping on the next flight from Raqqa to New York.

Anyone with a Syrian passport, real or fake, would still need to apply for a U.S. Visa before entering the country. American officials are currently reviewing immigration records to check whether someone with a fake passport could have already entered.

The threat of ISIS using fake passports is also hardly new. Syria has long been awash in forged and stolen passports. Numerous journalists have documented the process of obtaining one, which can cost less than a thousand dollars and take fewer than 48 hours.

It’s also unclear whether the new threat will have reverberations in the political field either. The parties are split on whether to accept Syrian refugees, and the spectre of an ISIS-fighter entering on a forged passport could easily play into the hands of those hoping to curtail immigration.

The release of the report and Comey’s testimony come as Americans are reporting the same level of fear of terrorism as immediately after the attacks of September 11th.