A letter sent this week by more than 130 House Republicans that expressed "grave concerns" about Homeland Security Secretary Alejandro Mayorkas’ suitability for office is the latest instance of Republicans in the chamber ramping up their oversight efforts on the DHS chief amid a spiraling border crisis – a push that has included rumblings of a possible impeachment.

"Your actions have willingly endangered American citizens, undermined the rule of law and our nation’s sovereignty," the 133 Republicans, led by Border Security Caucus co-chair Brian Babin, R-Texas., and Republican Study Committee Chair Jim Banks, said. "Your failure to secure the border and enforce the laws passed by Congress raise grave questions about your suitability for office."

TOP HOUSE REPUBLICANS QUESTION MAYORKAS ‘SUITABILITY FOR OFFICE’ AMID BORDER CRISIS

Signatures on the letter, first reported by Fox News Digital on Sunday, include Republican Leader Kevin McCarthy, Republican Whip Steve Scalise and House Republican Conference Chair Elise Stefanik. It comes as lawmakers on both sides of the aisle, and officials within the Biden administration, are warning of an even bigger migrant surge if the Title 42 public health order is lifted in May.

Notably, the lawmakers ask Mayorkas a number of questions, including whether he agrees that the Immigration and Nationality Act mandates the detention of illegal immigrants and whether he is obligated to "achieve and maintain operational control" over the border. The questions were much more concerned with Mayorkas’ understanding of his role, rather than specific requests for information

A senior House GOP aide told Fox News Digital that the letter shows that House Republicans are "focused on aggressive accountability and oversight of the Biden administration and of Secretary Mayorkas' failure at our southern border." 

Department of Homeland Security Secretary Alejandro Mayorkas testifies before the House Appropriations Subcommittee on Homeland Security on the Department of Homeland Security's budget request, on Capitol Hill in Washington, D.C., on April 27, 2022. (Photo by STEFANI REYNOLDS/AFP via Getty Images)

April 27, 2022: Department of Homeland Security Secretary Alejandro Mayorkas testifies before the House Appropriations Subcommittee on Homeland Security on the Department of Homeland Security's budget request, on Capitol Hill in Washington, D.C. (Photo by STEFANI REYNOLDS/AFP via Getty Images) (STEFANI REYNOLDS/AFP via Getty Images)

"Mayorkas must answer these basic questions because the American people want and deserve the truth about how he's run the Department of Homeland Security and whether he has followed the law as drafted and enacted," they said.

The letter did not explicitly mention impeachment, but its language immediately sparked speculation about whether the Republican caucus, including its leadership, is setting the stage for that eventuality. A statement by Babin mentioned Mayorkas being "removed" from his position.

"Secretary Mayorkas has repeatedly shown a blatant disregard for our laws and refuses to put radical politics aside and secure our country," Babin said. "He must immediately rectify his dangerous policies and uphold his constitutional obligation to protect our borders, or he should be removed from his position. Our safety and sovereignty are at stake."

Rep. Chip Roy, R-Texas, has repeatedly circulated a memo to his fellow lawmakers making the case for impeachment. He told Fox News Digital in an interview that his colleagues have been considering the memo for a while, but acknowledged there is a "cultural, and I’d say principled and legal hesitancy or resistance among Republicans in particular to want to venture down the road of the use of impeachment generally." He also said there is a "misperception" that impeachment needs to be tied to a specific violation of a statute.

"[Mayorkas is] still violating his oath and that oath to carry out the laws of the United States and execute the laws, faithfully execute the laws," Roy said. "He is purposefully avoiding the use of the tools at his disposal to do what the law commands that he does as secretary, which is to maintain operational control at the border."

Roy believes the attitude among Republicans is changing as the situation at the border gets worse.

"Republicans are starting to look at this and go: Good grief, this is just the height of irresponsibility, and it’s resulting in dead Americans and a weakened country and a narcoterrorist state in Mexico," he said. "How is this not exactly what the founders intended in terms of the Congress being able to exercise its right to call out an administration for failing to execute its laws?"

Mayorkas and DHS have defended its handling of the border crisis, putting out a plan to handle the end of Title 42, and urging Congress to "pass legislation that holistically addresses the root causes of migration, strengthens border security, fixes our immigration system, and improves legal pathways,"

Roy called the administration’s plan to handle the post-Title 42 migrant surge "bullsh--" and referred to the order, which allows for the rapid expulsion of migrants at the border, a "Band-Aid on a gunshot wound."

"It’s the bare minimum you should be doing in a world in which you are refusing to enforce the law and secure the border," he said.

However, at the same time, Republicans have stressed that impeachment is just one of a broad range of options available to them to hold Mayorkas accountable for what they see as his role in exacerbating the crisis at the border -- and are already starting to carefully build that case for whatever action they may choose to take.

"Secretary Mayorkas isn’t an ordinary cabinet official. His intentional lawbreaking has cost countless American lives," Rep. Banks said in a statement to Fox News. "There’s widespread agreement that he must face consequences and Republicans are building a case and exploring avenues to hold Secretary Mayorkas accountable for his role in creating one of the worst humanitarian crises in American history."

DHS PUBLISHES PLAN TO DEAL WITH POST-TITLE 42 MIGRANT SURGE AMID BIPARTISAN PUSHBACK 

Republicans have been hammering DHS agencies for requests for information since the border crisis accelerated in early 2021 and have been frustrated with the responses. Now, with the end of Title 42 looming and migrant numbers spiking to historic highs (there were more than 221,000 migrant encounters in March alone), Republicans are sounding that alarm even louder.

McCarthy said in a press conference at the border this week, said that while impeachment was an option, they were focused on starting by getting the answers to the questions they submitted -- for which they have given him 30 days to respond.

"So [Mayorkas] can't sit there like he's done time before and say, let me get back to you. There's no time for getting back to us. And it's not about answering us. It's about answering the American public. This is his moment in time to do his job. But at any time, if someone is derelict in their job, there is always the option of impeaching somebody. But right now, he's got 30 days."

Republicans are expected to regain control of the House in November, giving them the control of committees in 2023, which would arm them with a number of tools for oversight. 

Roy told Fox that he has always viewed impeachment as "just one of the tools" to hold Mayorkas accountable: "I don't even have any personal animosity toward Mayorkas, all I know is -- the border is not secure, they are failing and that needs to end."

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He also warned his fellow lawmakers that they would be punished at the ballot box if they didn’t rise to the occasion.

"They’ve got to throw every ounce of their being into securing the border of the United States or Americans are going to throw every ounce of their being into kicking their a-- to the curb, and they should kick their a-- to the curb, including me, if we don’t throw our entire bodies in front of the trainwreck that is our open borders."