The head of U.S. Customs and Border Protection on Sunday defended his embattled agency after the second death of a migrant child in its custody in less than a month — even as a top Senate Republican promised hearings on the matter.

Appearing on ABC News’s “This Week,” Commissioner Kevin McAleenan said the deaths of the two children, both from Guatemala, were“just absolutely devastating for us on every level.” But he also said everything was done to care for the children’s well-being and prevent the tragedies.

“What I can tell you about these two cases — and I’ve looked at our operation reporting, the initial investigative reporting, I looked at the fathers’ statements and interviews — is that our agents did everything they could as soon as these children manifested symptoms of illness to save their lives,” McAleenan said.

McAleenan then detailed what he knew about each case.

Of 8-year-old Felipe Gomez Alonzo, who died last week: “In Felipe’s case, it was actually a Border Patrol agent who noticed his symptoms and made the decision to take him and his father to the emergency room, where he had the treatment of doctors in Alamogordo, New Mexico.”

Of 7-year-old Jakelin Caal, who died early this month: “Jakelin was 94 miles away from the nearest Border Patrol station. She started to vomit on a bus ride to that station. Our agents got her there as quickly as they could, where we had a paramedic waiting — an agent who’s a paramedic, too — to revive her and get her into emergency medical service and life-flight her to a children’s hospital in El Paso.”

Jakelin’s father, Nery Caal, has said that neither he nor his daughter were provided water for eight hours while in custody at a remote border facility — a claim that contrasts what CBP has said.

The deaths have reignited a rancorous debate over the Trump administration’s now-abandoned policy involving the separation of migrant families at the U.S. border with Mexico. Even before the deaths, Democrats and many Republicans decried the policy as inhumane and unnecessary. Its adherents have defended it as abiding by the letter of the law and have said it was necessary for border security, because parents can’t be held in custody with their children and would otherwise be released.

It is also increasingly coloring the debate over the nine-day-old government shutdown, in which Trump is demanding funding for a border wall and Democrats have declined his request.

Trump weighed in on the children’s deaths for the first time Saturday on Twitter, opting to blame Democrats rather than offer condolences.

“Border Patrol needs the Wall and it will all end,” Trump tweeted.

White House counselor Kellyanne Conway echoed Trump on Sunday, telling CNN’s “State of the Union” that the deaths were tragic but that Democrats were using the children as “political pawns.”

“The president does not want these children to come on the perilous journey to begin with,” Conway said. “They are paying now; some of them are paying the ultimate price.”

On the same program, incoming chairman of the Senate Judiciary Committee, Lindsey O. Graham (R-S.C.), said he would hold hearings on the deaths. But he suggested it would focus on the root causes of such families' journeys.

“Yes, I’m going to hold hearings on the deaths of these two children and the policies that entice people to come,” Graham said.

The senator added: “Right now, we have 11,000 unaccompanied minors from Central America; 98 percent of them never leave. In 2014, [Sen.] Dianne Feinstein [D-Calif.] asked President Obama to change our policy. We have an unaccompanied minor from Central America, they should be sent back to their home country, just like if they were from Mexico. That’s a legal change we need to make with this [shutdown-border wall] deal.”