(NewsNation) — Attorney General Merrick Garland testified Wednesday morning before the Senate Judiciary Committee as it continues its investigations into the current and former presidents.

Garland was grilled by senior Republican members of the committee about the fentanyl crisis, the flow of drugs and migrants over the U.S.-Mexico border and the Hunter Biden investigation among other topics.

It was a highly contentious hearing at times involving Republicans and the attorney general, but the main issue of consensus centered around turning around the fentanyl crisis, which the attorney general described as an epidemic.

When asked to describe the fentanyl problem in America, Garland said, “It’s an epidemic that’s been unleashed on purpose by the Sinaloa and the new generation Jalisco cartels.”

Questions were launched from both sides of the political aisle over how the Justice Department (DOJ) is responding to the fentanyl crisis.

Senator Lindsey Graham, R-S.C., the ranking member of the Judiciary panel, asked if Garland agrees that “whatever we’re doing is not working.”

Garland replied, “I agree with that because of the number of deaths you pointed out.” 

Garland also said Mexico’s government needs to further step up.

“They are helping us but they could do much more,” he said. “There’s no question about that.”

Graham pressed Garland on designating Mexican drug cartels as terrorist organizations, according to The Hill.

Garland said he had no objection, but cautioned that such a decision is up to the State Department.

The White House would not say if President Joe Biden would support such a change. The White House would not back the possibility, which Garland embraced, that top cartels could be designated as foreign terrorist organizations.

The attorney general did agree with Graham that sentencing restrictions might need to be strengthened to act as a potential deterrent for dealers.

The hearing titled “Oversight of the Department of Justice” was the panel’s first oversight hearing of the Justice Department in the 118th Congress and comes at a significant moment for the DOJ, which is overseeing a number of probes into top political figures.

Garland vowed Wednesday he won’t interfere with an investigation into Hunter Biden’s taxes, a probe that’s continuing to unfold as congressional Republicans intensify their focus on the president’s son.

Garland told the Senate panel he has left the matter in the hands of U.S. Attorney David Weiss, the top federal prosecutor in Delaware, who would be empowered to expand his investigation outside the state if needed.

“He has been advised he is not to be denied anything he needs,” Garland said. “I have not heard anything from that office to suggest that they are not able to do everything the U.S. Attorney wants to do.”

The Hill and the Associated Press contributed to this report.