Fake Syrian passports have already been discovered in Europe, most notably, the two used by suicide bombers in the horrific terrorist attack on Paris last month.
The terror group ISIS may have access to passport printing machines and blank Syrian passports, says a media report. It adds that some followers of the organisation may have entered the US using authentic-looking passports.
A 17-page US Homeland Security Investigations Intelligence Report, issued to law enforcement last week, said ISIS likely has been able to print legitimate-looking Syrian passports since taking over the city of Deir ez-Zour, home to a passport office with "boxes of blank passports" and a passport printing machine, ABC News reported.
Another passport office was located in Raqqa, Syria, which has long been Islamic State in Iraq and Syria's de facto capital.
"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 travelled to the US," the report is quoted as saying.
The report notes that the primary source for the information was rated at "moderate confidence", the second-highest rating given for source assessments.
Testifying before lawmakers on Wednesday, FBI Director James Comey first publicly talked about the nation's top security officials' anxiety over the problem.
"The intelligence community is concerned that they (ISIS) have the ability, the capability to manufacture fraudulent passports, which is a concern in any setting," Mr Comey said.
Fake Syrian passports have already been discovered in Europe, most notably two used by suicide bombers in the horrific terrorist attack on Paris last month. The two men are believed to have slipped into Europe with a flood of Syrian refugees fleeing the violence in their homeland.
According to the source that provided the passport information to homeland security officials, Syria is awash in fake documents.
"The source further stated that fake Syrian passports are so prevalent in Syria that Syrians do not even view possessing them as illegal," the report was quoted as saying.
"The source stated fake Syrian passports can be obtained in Syria for USD 200 to USD 400 and that backdated passport stamps to be placed in the passport cost the same," it said.
The report said it is unclear what state the "blank" passports stolen from Deir ez-Zour were in or if they were completely blank. It also notes that the "whereabouts of the passport machine(s) remain fluid."
"If ISIS ability to produce passports is not controlled, their operations will continue to increase and expand outside of their operational controlled areas," the report concluded.