Hundreds of illegal immigrants attempting to cross the southern border as part of massive migrant caravans were found to have criminal histories in the U.S., according to newly obtained Department of Homeland Security documents.

The DHS files were provided to House Oversight Committee Republicans in May and included internal data showing more than 1,000 migrants traveling as part of caravans to the border within the past nine months had “U.S. criminal histories” and hundreds had “U.S. criminal convictions.”

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The files detailed one migrant caravan of nearly 8,000 individuals that started toward the border in October 2018 and arrived south of California by December. According to U.S. Immigration and Customs Enforcement (ICE), 660 of them had U.S. criminal convictions—with 40 convicted of assault or aggravated assault with a deadly weapon, and three convicted of murder.

In January 2019, U.S. Customs and Border Protection (CBP) tracked another caravan that left Honduras with more than 3,300 migrants. ICE’s Homeland Security Investigations (HSI) team identified that 860 of those individuals had U.S. criminal histories, including more than 20 convicted of assault or aggravated assault with a deadly weapon, nearly 30 convicted of sexual offenses, two convicted of violence against law enforcement, and one convicted of attempted murder.

The documents, provided to House Oversight Republicans, also revealed that CBP is currently monitoring another “movement of several groups ranging in size from 1,000 to 4,000” in the Mexican states of Chiapas and Veracruz, but did not specify how many of those migrants are believed to have criminal records.

In a letter to DHS Acting Secretary Kevin McAleenan on Thursday, committee Ranking Member Jim Jordan, R-Ohio, requested further information about caravan members with criminal backgrounds to “assist” in their “oversight of the crisis at the southern border and better understand the threat posed by large caravans.”

Jordan requested arrest warrants, court documents and other materials detailing the criminal histories of the migrants in the January 2019 and October 2018 caravan; an update of CBP’s monitoring of the caravan movement in Mexican states; and summaries of ICE HSI materials by July 5.

In his letter, Jordan referred to President Trump’s decision in February to declare a national emergency and referred to his comments that the “southern border is a major entry point for criminals, gang members, and illicit narcotics” threatening “core national security interests.”

The newly revealed DHS information comes amid a stunning surge across the border this year. Last month, the number of migrants apprehended at the southern border skyrocketed to levels not seen in over a decade, with CBP reporting nearly 133,000 arrests in May. The number surpassed 144,000 when counting migrants deemed inadmissible—more than a 30 percent increase from the prior month and double the influx recorded at the beginning of the year. The number was the highest monthly total in more than 13 years, officials said.

“We are in a full-blown emergency,” Acting CBP Commissioner John Sanders said earlier this month. In April, authorities recorded 99,304 arrests.

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McAleenan, in testimony before the Senate Judiciary Committee last week, also warned that 90 percent of asylum seekers skip their hearings after being released into the U.S.

The continued crisis at the border comes as Trump has sought to extend and shore up the border wall, declaring a national emergency in a bid to divert billions toward construction -- an effort being challenged in the courts.

Meanwhile, the Trump administration announced that it had reached a deal with Mexico to drop threatened tariffs on Mexican imports in exchange for Mexico increasing efforts to limit U.S.-bound migration flows from Central America.

Through the agreement, the U.S. is slated to extend its policy of returning asylum applicants to Mexico while their claims are processed. The U.S. also committed to accelerating asylum claims while Mexico said it will “offer jobs, healthcare, and education according to its principles.”

The deal also stated that Mexico will take “decisive action” to dismantle smuggling and trafficking operations, while both countries will increase cooperation to protect the border.

Fox News' Adam Shaw contributed to this report.