() More than 3,500 people were arrested during Immigration and Customs Enforcement (ICE) operations in President Donald Trump’s first week back in office.

More than half of those arrests took place over the weekend as the administration bolstered security with more than 1,500 active-duty troops and some 25,000 National Guard and Army Reserve troops stationed along the nation’s southern border.

Arrestees will soon outnumber the government’s holding facilities, said Patrick J. Lechleitner, who served as Immigrations and Customs Enforcement director under President Joe Biden.

“I mean, we’re only appropriated for 41,500 beds up until the new administration came in,” Lechleitner said. “That’s [for] holding, from what I understand.”

“Ultimately, it’s resource-driven. Do we have the facilities? Do we have the bed space? We’re going to require a lot more resources and money to do that. That’s in Congress’ hand, quite frankly,” Lechleitner told .

Right now, Congress is putting its focus on investigating “sanctuary cities” like Chicago, Boston, New York and Denver, whose leadership has refused to comply with Trump’s plans for mass deportations.

On Tuesday, the House Oversight Committee sent letters to the cities’ mayors requesting more information about their efforts to assist with the raids.

Rep. James Comer, R-Ky., chair of the committee, called for the mayors to testify before Congress next month.

“Congress must determine whether further legislation is necessary to enhance border security and public safety,” Comer said in a statement Monday.

It’s not yet confirmed whether the leaders will agree to appear before the committee.

‘s Mills Hayes contributed to this report.