Approximately 220,000 illegal immigrants have evaded Border Patrol since October, a Department of Homeland Security official told Fox News on Wednesday, coming during months that are typically slower for border crossings.

The source said that there are approximately 220,000 known "gotaways", meaning those who get past Border Patrol when coming across the border. That number is separate from encounters, in which Border Patrol has either caught the migrant or the migrant has turned themselves in.

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Known gotaways are those who have been spotted on cameras and sensors etc., but Border Patrol does not have the manpower to get to. It is harder for officials to estimate the number of "gotaways" who have avoided detection altogether -- meaning the number of actual gotaways is likely much higher.

That 220,000 come during the traditionally slower months at the border, meaning those numbers, along with the number of those encountered, are likely to ramp up significantly as the spring and summer months approach.

The number of encounters are the border are also high, and indicate a busy season ahead. Customs and Border Protection (CBP) announced last week that there were 153,941 migrant encounters in January 2022. In January 2021, there were 78,414 migrant encounters.

An earlier court filing also revealed that 62,573 migrants were released into the United States in January. In December 2021, there were 178,840 migrant encounters and 173,620 in November.

The Biden administration has stuck fast to strategy of targeting "root causes" in Central America, while opening up asylum pathways. But Republicans have accused the administration of fueling the crisis by rolling back Trump-era border protection policies like border wall construction and the Migrant Protection Protocols (MPP).

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While the Biden administration was forced by a federal court to reinstate MPP, which kept migrants in Mexico for their hearings, it has sought to end the program by an alternative route. Meanwhile, it has called for amnesty for illegal immigrants already in the country, and has also dramatically narrowed interior enforcement by Immigration and Customs Enforcement (ICE.)

While the administration has defended its record on the border, blaming the Trump administration for closing asylum pathways and warning that its own root causes approach won’t fix the crisis "overnight." 

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Republicans have become increasingly impatient with the crisis -- with attorneys general and lawmakers in the House recently calling for DHS Secretary Alejandro Mayorkas to resign over the crisis.