WASHINGTON (AP) — Homeland Security Secretary Alejandro Mayorkas faced a barrage of criticism Wednesday from House Republicans who, in recent months, have floated impeaching him over what they say is his dereliction of duty in securing the southern border.

Mayorkas' appearance before the House Judiciary Committee comes as the Biden administration's immigration policies are facing legal attacks from across the political spectrum, despite a steep drop last month in the number of border crossings.

"I know that today Secretary Mayorkas is going to try to paint a rosy picture of this disastrous mismanagement of our border," Ohio Rep. Jim Jordan, the Republican chair of the Judiciary Committee, said in his opening statement. "But the numbers don't lie."

Jordan and other Republicans attributed the sudden falloff in migrant crossing to a new Biden administration asylum policy that allows migrants to use a Customs and Border Patrol app when seeking asylum. The new technology is attempting to streamline the asylum process by allowing more people — on average 1,400 a day — to get an appointment through the app before appearing at a U.S. port of entry with an asylum claim.

"That's why the numbers are dropping," said Republican Rep. Tom McClintock of California.

Mayorkas pushed back on the GOP line of questioning and defended his department, which employs more than 260,000 people, for the "selfless" work they have done while facing unprecedented challenges both at the southern border and across the country.

"Our approach to managing the borders securely and humanely — even within our fundamentally broken immigration system — is working," Mayorkas said.

The secretary said illegal border crossings have been falling since the peak that came before Title 42, a public health law allowing curbs on migration in the name of protecting public health. The policy was instituted under former President Donald Trump in March 2020 as part of an effort to prevent the spread of COVID-19. The Biden administration ended Title 42 in May.

Since then, total encounters along the southern border — meaning migrants who either came to one of the ports of entry or tried to cross between them — were down 30% in June compared with the previous month. DHS said it was the lowest monthly total since February 2021.

The Biden administration has said the asylum rule was a key part of its strategy to strike a balance between strict border enforcement and ensuring several avenues for migrants to pursue valid asylum claims.

And the secretary implored Congress on Wednesday to join his department and work as "partners" in creating long-term, sustainable solutions to what both sides agree is a flawed immigration system.

But Republicans zeroed in on the influx of fentanyl into the country, blaming Mayorkas for the number of overdoses that have happened across American communities in the past several years.

"The fentanyl killing thousands of Americans every year is a direct result of your dereliction," said Rep. Ken Buck, R-Colo., "When people die of fentanyl poisoning, it is your fault."

The agency, Mayorkas responded, have stopped nearly 10,000 pounds of fentanyl from entering the country last year, leading to more than 280 arrests.

Democrats pressed Mayorkas on how fentanyl is getting into the U.S. and spreading across the country. He said much of the smuggling is done by Americans.

"I believe the data suggests that approximately 70% of the people who are arrested are US citizens," Mayorkas testified.

But Republicans insisted Mayorkas is broadly responsible for deaths from fentanyl, despite those factors.

"In my mind, this makes your actions criminal," Rep. Jeff Van Drew, R-N.J., said. "Secretary Mayorkas you must resign. Will you resign?" Mayorkas said he would not.

Van Drew replied that it "leaves us with no other option: you should be impeached."

Republicans proposed impeaching Mayorkas well before they won the House majority last November. This year, Jordan and the GOP chairman of the Homeland Security Committee, Rep. Mark Green of Tennessee, have been conducting a multi-step investigation into the situation at the southern border.