The Obama administration has been placing illegal immigrant children with U.S. guardians who have previously been charged with a number of crimes, including child molestation, homicide, domestic violence and human trafficking, two senators alleged Tuesday, citing a whistleblower.

At least 3,400 sponsors of 29,000 in a government database had criminal histories, but federal officials refused to remove the immigrants from the homes even after the whistleblower alerted officials, said Senate Judiciary Chairman Charles Grassley, R-Iowa, and Sen. John Cornyn, R-Texas, reported The Washington Times.

"The whistleblower brought the claims to the Judiciary Committee's attention after raising concerns with supervisors reportedly yielded no immediate corrective actions," Grassley's office said in a statement, according to The Los Angeles Times.

"Although the whistleblower claims to have relayed these concerns to supervisors in August of 2015, apparently these individuals have no immediate plans to remove [unaccompanied minors] from their criminal sponsors, but are 'discussing options,'" the senators wrote in a letter to Homeland Security Secretary Jeh Johnson and Health and Human Services Secretary Sylvia Mathews Burwell, whose departments are responsible for processing the youths.

Federal "regulations prohibit [unaccompanied minors] from being released to a sponsor if there is substantial evidence that the child would be at risk of harm. Yet, due to a breakdown with screening and background checks of sponsors, many of the most vulnerable are being victimized."

The Health and Human Service's Office of Refugee Resettlement, which screens potential sponsors, did not deny the figures and responded with a statement.

"It is not the practice of the Office of Refugee Resettlement to place unaccompanied children with sponsors who have serious criminal convictions," spokesman Mark Weber said, according to the L.A. Times. "The safety of the children is our primary concern and any allegation of even potential harm is taken seriously and will be investigated."

Officials say that sponsors undergo criminal history checks and sometimes even fingerprint checks, but human smugglers have managed to disguise themselves as sponsors, according to the senators.

"For example," the senators write, "in July of 2015, federal agents arrested human smugglers in Ohio for trafficking at least a half dozen Guatemalan boys to work on an egg farm. Reports claim that these UACs were placed with the traffickers who posed as sponsors, were confined to dilapidated trailers with no beds, worked 12 hours a day, and were threatened with death if they sought help. Apparently, ORR has struggled to ensure that UACs are not placed with criminals since 2013, when it issued an alert warning of three 'fraudulent sponsors' with addresses in Colorado, Iowa, and Minnesota seeking to claim unrelated unaccompanied minors. It seems little corrective action has been taken, and many are still released into criminal hands."

The accusations come after last year's influx of more than 68,500 unaccompanied minors from Central America, which led to decreased oversight of the resettlement program, according to immigrant advocates. Just this week, Border Patrol statistics confirmed that another surge of illegal immigrants are crossing the southern border, with more than 25,000 immigrants and some 5,000 unaccompanied minors being caught since Oct. 1, a 58 percent increase from the same time last year, as HNGN previously reported.