Homeland Security Secretary Alejandro Mayorkas conceded Monday that the surge of the COVID-19 delta variant at the border took him by surprise.

Speaking virtually at the 18th Annual Immigration Law and Policy Conference at Georgetown University, Mayorkas said, "What I didn't expect was the tragic rise of the delta variant. And we took a step back by reason of that. I did not expect to be in late September where we are."

"We are confronted with a population of people that, as a general matter, that have a rate of illness of approximately 20%," he continued. "When one is speaking of 7,000 or 7,500 people encountered at the border every day, if one takes a look at that the system, it is not built for that in a COVID environment where isolation is required."

Mayorkas' comments came a day after he told "Fox News Sunday" host Chris Wallace that approximately 12,000 Haitian migrants have been released into the United States amid the surge at the border in recent weeks.

"Approximately, I think it's about 10,000 or so, 12,000," Mayorkas said regarding the number of those released. He also said that number could increase after 5,000 other cases are processed.

"It could be even higher. The number that are returned could be even higher. What we do is we follow the law as Congress has passed it," he added.

MAYORKAS SAYS AS MANY AS 12K OUT OF 17K MIGRANTS HAVE BEEN RELEASED INTO US, AND ‘IT COULD BE HIGHER’

Former President Trump released a statement Sunday blasting the Biden administration for releasing the migrants, claiming they are doing so "with no vetting, checking or even minimal understanding of who they are."

CLICK HERE TO GET THE FOX NEWS APP

"Some are very sick with extremely contagious diseases, even worse than the China Virus. They are not masked or mandated, but just let free to roam all over our Country and affect what was just a year ago, a great Nation," Trump said.