Terrorists are constantly seeking to exploit immigration systems to enter the United States and the refugee stream is particularly vulnerable, according to an internal Immigration and Customs Enforcement memo obtained by Congress.

“[The] Refugee Program is particularly vulnerable to fraud due to loose evidentiary requirements where at times the testimony of an applicant alone is sufficient for approval,” the ICE document reads.

“As a result, a range of bad actors, who use manufactured histories, biographies and other false statements, as well as produce and submit fictitious supporting documentation, have exploited this program,” it adds.

House Judiciary Committee Chairman Bob Goodlatte and House Oversight and Government Reform Committee Chairman Jason Chaffetz made the details of the memo public Thursday in a letter to Homeland Security Secretary Jeh Johnson.

In their letter, the committee chairmen expressed concerns about the Obama Administration’s plan to raise refugee admissions to 110,000 in FY 2017 and increase the number of Syrian refugees admitted to the United State beyond the 13,000 admitted this fiscal year.

“The President’s decision to increase overall refugee resettlement-and specifically that of Syrian refugees-ignores warnings from his own national security officials that Syrians cannot be adequately vetted to ensure terrorists are not admitted,” the pair wrote. “Revelations about fraud, security gaps, and lack of oversight have demonstrated that the program is creating national security risks.”

Of particular concern and their reason for writing to Johnson, they explained, is that the internal ICE document their committees obtained “confirms those serious concerns.”

Goodlatte and Chaffetz’s letter offers key excerpts from the ICE memo including:

– The Immigration System is a constant target for exploitation by individuals who seek to enter the United States and who are otherwise ineligible for entry based on security grounds. The Refugee Program is one such avenue in which ineligible aliens seek to enter by fraud. -In many instances, the applicant for a benefit (including both asylum and refugee status) receives a government issued document that contains the biographic information that the applicant supplied. This document can be used for many things, such as obtaining a driver’s license. -Identity fraud can be prevalent in the refugee process. The uniform processing of refugees by the Dep (DHS) offices takes places in foreign refugee camps. Typically, these camps have been established outside of war zones and many have open access, thereby allowing individuals to infiltrate and purchase the identities of those individuals already in the process. – Refugee fraud is easy to commit, yet not easy to investigate [because] [r]efugee laws purposefully contain relaxed evidentiary requirements . . . , Refugee applications do not require sponsorship of a third party, such as a relative or employer, [and] Refugee claims are typically made in areas of the world where it is difficult to investigate the veracity of the claim.

Goodlatte and Chaffetz demanded to know if the internal memo was considered while the administration was deciding to lift the refugee cap by 30 percent, when Johnson received the memo, if it has been shared with other agencies, and how the department plans to address the apparent security gaps. They requested an answer to their questions by Oct. 4, 2016.