The number of migrant family units encountered at the southern border increased by nearly 50% in July, with only a fraction of them being removed under Title 42 health protections -- part of a broader surge in numbers that Homeland Security Secretary Alejandro Mayorkas has called "unsustainable."

There were 82,966 encounters of individuals coming as part of a family unit in July, up from 55,839 in June. It means that so far there have been 328,121 family unit encounters so far this fiscal year.

MAYORKAS ANNOUNCES 212,672 MIGRANT ENCOUNTERS IN JULY, SAYS BORDER ‘IS ONE OF THE TOUGHEST CHALLENGES WE FACE’ 

For comparison there were just 7,296 migrant family encounters in January.

It's part of an overall 212,672 encounters in July, a 13% increase over June and considerably higher than the 78,417 encountered in January and the 40,929 encounters in July 2020.

MASSIVE BORDER NUMBERS FORCE OFFICIALS TO KEEP ADDING LAYERS TO STAT CHART

Announcing the numbers on Thursday, Mayorkas said that only 12% of those encountered had been removed via Title 42 -- which allows for the rapid expulsion of migrants due to COVID-19. The Biden administration extended the Trump-era order earlier this month, but has largely not been applying it to migrant families due to Mexico's refusal to take them back.

In a release, CBP noted that the numbers encountered are just below the peak of 88,587 in May 2019 during that year’s border crisis, and that the total number of family unit encounters is still lower than the same period in FY 2019.

MAYORKAS SAYS BORDER CRISIS ‘UNSUSTAINABLE’ AND ‘WE’RE GOING TO LOSE' IN LEAKED AUDIO 

However, Mayorkas has admitted the situation is grim, calling the border situation "one of the toughest challenges we face."

"It is complicated, changing and involves vulnerable people at a time of a global pandemic," he said.

However, privately he was more dour in his assessment when he spoke to Border Patrol agents.

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"A couple of days ago I was down in Mexico, and I said look, you know, if, if our borders are the first line of defense, we're going to lose and this is unsustainable," Mayorkas said, according to leaked audio obtained by Fox News. "We can't continue like this, our people in the field can’t continue and our system isn't built for it."

Fox News’ Bill Melugin contributed to this report.