FIRST ON FOX: Sen. Chuck Grassley, R-Iowa, is calling for answers from the Department of Homeland Security (DHS) on new data he says shows an "alarmingly low" percentage of DNA samples of illegal immigrants being received by the FBI.

Grassley, in a letter to Customs and Border Protection (CBP) acting Commissioner Troy Miller and Homeland Security Secretary Alejandro Mayorkas, cites whistleblower data his office has received related to CBP DNA collection practices of immigrants arriving at the northern and southern borders.

"Those disclosures show that in the first three quarters of FY23, FBI received an alarmingly low percentage of DNA samples," he wrote.

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Sen. Chuck Grassley speaks into mircrophone during hearing

Sen. Chuck Grassley, R-Iowa, has obtained whistleblower information on DNA testing at the southern border. (Al Drago/Bloomberg via Getty Images)

The statistics he cites show that in Q1 of FY23, there were 865,333 migrant encounters, and 347,231 DNA samples were received by the FBI -- about 40%

In Q2, just 31.21% were received by the FBI and in Q3 that number was 37%. He said he had previously requested FY 23 data but had not received it.

"Given the record number of illegal crossings, CBP encounters, and ICE detainees with prior criminal records, CBP and DHS’s continued failure to collect DNA on illegal immigrants is deeply concerning," he said. "This failure weakens our justice system and empowers criminals to illegally cross our border, jeopardizing American lives." 

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Grassley has previously noted that the Justice Dept. removed exemptions from the 2005 DNA Fingerprint Act in 2020, broadening the number who can be fingerprinted. There are still exemptions for under 14-year-olds and those who already have a DNA profile, according to a recent Government Accountability Office (GAO) report.

However, the government has also been dealing with a shortage of test kits, although CBP now says it has a sufficient number of kits, and Republicans recently highlighted a reported 15-month backlog on DNA testing. CBP collects DNA samples via a Buccal Collection kit for submission to the FBI's Combined DNA Index System (CODIS) from those arrested on federal criminal charges and for those detained by CBP who are not exempt. 

CODIS "blends forensic science and computer technology into a tool that enables federal, state, and local forensic laboratories to exchange and compare DNA profiles electronically, thereby linking serial violent crimes to each other and to known offenders," CBP says. CODIS is also used by the National Missing Persons DNA Database to help identify missing and unidentified individuals. 

CBP also collects biometric data from some noncitizens, including fingerprints – as well as biographical information including documents and addresses, which is checked against available data systems. CBP says that, consistent with the 2005 legislation, it collects samples for CODIS submission "from all persons in CBP custody who are subject to fingerprinting, unless otherwise exempt." 

Grassley cites a number of reports that show examples of crimes illegal immigrants have been connected to via DNA matches, including unsolved cases, even with what he called "insufficient" DNA efforts by federal authorities.

In his letter, Grassley asks for a range of information, but he specifically asks whether Jose Antonio Ibarra -— who was recently charged in the murder of Georgia student Laken Riley and who has since been confirmed to be an illegal immigrant released into the U.S. last year — was ever subject to a DNA sample.

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He also requests data for Q4 and for FY 24 so far, as well as additional plans to implement the DNA Fingerprint Act. 

CBP told Fox that it responds to congressional correspondence directly via official channels and cannot comment futher on an ongoing criminal investigation.

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The letter comes as illegal immigration is set to be a top 2024 issue. President Biden and former President Donald Trump both visited the southern border in Texas last week as polling shows it is a top concern for voters.

CBP sources tell Fox News that there have been more than 21,000 migrant encounters in the past 72 hours, with Tucson Sector being the busiest with more than 5,400. It’s in line with traditional surges as numbers increase as the Spring arrives, but the numbers suggest it is going to be a significant surge.

Fox News' Griff Jenkins contributed to this report.