(NewsNation) — The ongoing crisis at the southern border has defined much of Homeland Security Secretary Alejandro Mayorkas‘ first two years in office, and for the third time in six months, he will testify before lawmakers on Capitol Hill.

Mayorkas is scheduled to attend a Senate Judiciary Committee hearing Tuesday. The appearance comes just one week after DHS launched “Operation Blue Lotus,” a new plan to crack down on fentanyl entering the country.

Republicans in Washington have remained highly critical of Mayorkas, with some going as far as filing articles of impeachment against the secretary whose time in office has coincided with a surge of illegal border crossings.

border encounters near historic highs

Since Mayorkas took over DHS in February 2021, migrant encounters along the southwest border have hit record highs, increasing to more than 250,000 in the month of December alone. That number has fallen almost 40% in recent months, down to 155,000 in February.

It’s a trend Mayorkas has pointed to as a sign President Joe Biden’s recently enacted enforcement measures have been effective.

In January, Biden announced the U.S. would immediately begin turning away Cubans, Haitians and Nicaraguans who cross the southern border illegally. DHS officials also said they would begin denying asylum to those who did not first ask for asylum in the countries they traveled through to get to the U.S.

Despite the decline at the start of 2023, border encounters in January were still 300% above the same month in 2020 before the COVID-19 pandemic.

In total, federal agents have encountered more than 4.8 million migrants at the southern border since Mayorkas took office.

terrorist watchlist encounters up

Although they still represent a tiny fraction of all encounters, border patrol agents have stopped significantly more individuals on the federal terror watchlist as of late.

From 2017 to 2020, border patrol agents recorded just 11 terror watchlist encounters between ports of entry along the U.S.-Mexico border. Last year, that number rose to 98. At the current rate, the 2023 fiscal year is on pace for more than 160 such encounters.

Republicans on Capitol Hill have drawn attention to the recent uptick, and some have called on Mayorkas to resign.

The terror watch list has an estimated 2 million names of people who represent a potential threat to the United States.

fentanyl seizures are up

In November, CBP seized a record-high 2,900 pounds of fentanyl along the southern border. Just three years ago, border authorities were seizing around 380 pounds of fentanyl per month.

The deadly drug has become a cash cow for Mexican drug cartels who are fueling an opioid epidemic that killed over 80,000 Americans in 2021.

In response, DHS recently launched “Operation Blue Lotus” to detect and seize fentanyl coming into the United States. In its first week, the operation led to 18 seizures, 16 federal arrests and two state arrests that stopped more than 900 pounds of fentanyl from entering the U.S., DHS said.

Mayorkas announced the operation during a border visit in Arizona last week where he highlighted his department’s record seizures while also acknowledging that it must do more.