EXCLUSIVE: Sen. Ron Johnson, R-Wis., is requesting more information on how many, and what kind of, criminal illegal immigrants are coming through the southern border amid the massive amounts of migrants being encountered by Customs and Border Protection (CBP).

In a letter to acting CBP Commissioner Troy Miller, Johnson is requesting data "on apprehensions of criminals, including confirmed gang members, at the southern border."

MIGRANT ARRESTS AT SOUTHERN BORDER ROSE YET AGAIN IN JUNE TO 188,000, TOPPING 1M THIS FISCAL YEAR

So far in FY 2021, there have been 7,830 "criminal noncitizens" arrested at the border, which already dwarfs the 2,438 criminals apprehended in FY2020 and is higher than the 4,269 encountered in FY2019. That increase comes amid a migrant surge that saw more than 188,000 migrant encounters in June, and more than a million in FY2021 so far.

Johnson, in his letter, outlined some of the increases in criminals with certain criminal convictions.

"From October 2020 to June 2021, apprehensions of individuals convicted of murder or homicide are up more than 10 times from the previous fiscal year; illegal weapons possession, transport, or trafficking are up more than 10 times from the previous fiscal year; assault, battery, and domestic violence are up more than four times from the previous discal year; and sexual offenses are up more than two times from the previous fiscal year," he wrote.

Johnson also noted that there have been 249 apprehensions of gang members. Those include MS-13 members with extensive criminal history. There were 363 apprehensions in all of FY 2020, which was down from the 976 in FY 2019.

Border Patrol have reported a number of the arrests, including the notorious MS-13, or Mara Salvatrucha, gang. Border Patrol chiefs have warned that such gang members are trying to sneak through as part of large groups of migrants.

Johnson said the arrests "underscore the urgency needed to address the border crisis" and blamed the Biden administration’s "failure to enact policies to address the crisis at the border."

BORDER PATROL NABS GANG MEMBERS, INCLUDING ,MS-13, ATTEMPTING TO ENTER US AS PART OF MIGRANT WAVE

Johnson requests a breakdown of how many gang members had prior convictions and how many had attempted to enter as part of a large group, as well as the countries of origin of criminal illegal immigrants who had been arrested at the border in previous years. 

A CBP spokesperson told Fox the agency had received the letter and would respond to Sen. Johnson directly.

Additionally, Johnson requested information on how many apprehended criminals or gang members entered the U.S. as unaccompanied children. Johnson had grilled Sheriff Ed Gonzalez, President Biden’s pick to lead Immigration and Customs Enforcement (ICE), on the matter last week – warning that many such children are actually male teenagers, who are more likely to be gang members.

"We are letting people in who are potentially gang members, we are letting in people who are going to be trafficking drugs or human trafficking, isn't that your experience as Houston’s sheriff?" he asked.

"I'm always mindful of not profiling and not developing any stereotypes in my work," Gonzalez said.

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"That’s not profiling," Johnson responded.

Republicans have been pointing to the continued numbers of both migrants and criminal migrants as they call for the Biden administration to take tougher enforcement measures to slow the surge in numbers. 

Last week, Senate Republicans warned that ending Title 42 expulsions, as the administration is believed to be considering doing, would exacerbate the crisis.