Senate Republicans on Tuesday grilled President-elect Joe Biden’s pick to head the Department of Homeland Security, Alejandro Mayorkas, over “troubling issues” in how he handled the visa program for wealthy foreign investors during the Obama administration.

At the confirmation hearing before the Senate Homeland Security and Governmental Affairs Committee, Ohio Sen. Rob Portman asked about a Homeland Security inspector general report issued in 2015, when Mayorkas served as deputy Homeland Security secretary.

The report concluded that Mayorkas “exerted improper influence in the normal processing and adjudication” of EB-5 visas in cases that involved high-profile individuals, including Harry Reid, the Senate majority leader at the time.

“These were politically connected individuals, where you were in direct contact with them, going around the typical judicatory process,” Portman said. “Did you have concerns that your actions might be viewed as favoritism and special access?”

Wisconsin Sen. Ron Johnson, the panel’s outgoing chairman, chimed in about “some pretty troubling issues” raised in a letter at the time by Sen. Charles E. Grassley, R-Iowa, about the way Mayorkas handled the EB-5 investor program, which offers visa holders and their families the chance to seek permanent residency in exchange for investing heavily in U.S.-based job-creating enterprises.

“[Grassley’s] main issue in writing the letter to you is that you have not been forthright, you’ve not answered questions dating back to his oversight letters 2013,” Johnson said to Mayorkas.

Utah Republican Mitt Romney also questioned whether Mayorkas would recuse himself in future cases that may cast the appearance of favoritism in the investor program.

Mayorkas defended his actions, saying the EB-5 program had been “plagued by problems” when he originally took the helm of the U.S. Citizenship and Immigration Services, the DHS agency responsible for adjudicating immigration benefits.

“I became involved in a lot of cases because, as I said, the work of the U.S. Citizenship and Immigration Services is casework. And I did my job. And I learned of problems, and I fixed it,” said Mayorkas, a Cuban refugee who would be the first Latino to lead the Homeland Security Department if confirmed.

Mayorkas said he had gotten involved in handling certain cases to ensure that the cases were being dealt with properly.

Senate Democrats, including Delaware’s Thomas R. Carper, defended the nominee.

“Mr. Mayorkas was found to be guilty of one thing, and that’s creating an appearance of favoritism,” Carper said. “If we will be honest with one another, every single member of this committee and in the Senate could be accused of the same thing at one time or another.”

The last time Mayorkas faced a Senate confirmation hearing — in 2013, to become deputy Homeland Security secretary — not one Republican voted in favor of his nomination because of the active investigation into his handling of the EB-5 program.

Mayorkas was previously confirmed by the Senate to become director of the USCIS, where he served from 2009 to 2013. In that role, he led the implementation of the Deferred Action for Childhood Arrivals, or DACA, program that has allowed immigrants who came to the U.S. unlawfully as children to live and work in the country without fear of deportation.

The Senate also confirmed Mayorkas as U.S. attorney for the Central District of California earlier in his career.

Lawmakers on both sides of the aisle peppered Mayorkas with questions on border security and how he would handle asylum-seeking migrants reportedly heading in caravans to the U.S.-Mexico border.

Mayorkas said his plans include investing in more technology rather than spending money on border wall construction.

“The use of technology and use of air and marine assets would be most effective and I look forward to studying the challenges at the border and developing a sophisticated approach to meet those challenges to be sure that we’re harnessing innovation and technology to the best of our abilities,” he said.

Congress has appropriated nearly $1.4 billion in the current fiscal year for President Donald Trump’s border wall. Mayorkas said he would need to research laws about discontinuing funds allocated for a specific purpose.

On asylum, Mayorkas remained firm on upholding Biden’s commitment to ensuring that asylum seekers are humanely processed at the border.

“That means to provide humanitarian relief for those individuals who qualify for under the law, and that could not be accomplished with just a flick of a switch and turned on in Day One. … It will take time to build the infrastructure and capacity so that we can enforce our laws as Congress intended,” he said.

Incoming Senate Homeland Security Chairman Gary Peters urged his colleagues to immediately confirm Mayorkas because of ongoing threats the U.S. faces both at the border and within the country.

“There is no question, we need strong and stable leadership at the Department of Homeland Security, now more than ever,” the Michigan Democrat said. “Certainly, the threats that we face across all these borders happen daily, which is why his appointment to this position is absolutely critical to do it as quickly as possible.”

Shortly after the hearing ended, Republican Sen. Josh Hawley of Missouri announced he would not back the nominee because Mayorkas failed to “adequately” explain how he would secure the southern border.

“Just today, he declined to say he would enforce the laws Congress has already passed to secure the border wall system. Given this, I cannot consent to skip the standard vetting process and fast-track this nomination when so many questions remain unanswered,” he said in a statement Tuesday.

In addition to Mayorkas, other Biden picks receiving Senate hearings Tuesday included Defense Secretary nominee Lloyd Austin; Secretary of State nominee Antony Blinken; and Avril Haines, the nominee for director of national intelligence.