WASHINGTON (Nexstar) — Senate Republicans grilled Homeland Security Secretary Alejandro Mayorkas on the Biden administration’s response to the sharp rise in migrants arriving at the U.S.-Mexico border.

According to U.S. Customs and Border Protection, more than 178,000 migrants were apprehended at the U.S.-Mexico border in April — the highest monthly level in 20 years.

“We have the secretary responsible for securing our border and immigration system who doesn’t recognize these charts as being a problem,” said Sen. Mitt Romney (R-UT).

“Senator, we have taken immediate action with respect to the unaccompanied children,” Mayorkas said.

Mayorkas said because of the Biden administration’s quick response, there are now significantly fewer migrant children in U.S. custody.

“We are taking a look at the process, the system and how we can reengineer it for a better future,” Mayorkas said.

He told senators the Biden administration inherited the problem from the last administration, so any fix will take time.

“We speak of lawful pathways and in support of them, and yet the prior administration tore those down, too. They tore down the Central American Minors Program,” Mayorkas said.

Mayorkas said the current administration is focused on addressing why these children are coming to the U.S. in the first place.