Republican presidential nominee Donald Trump claimed during an appearance on Fox News that he had never heard of immigrant detention centers and would not use them as part of his immigration plan, despite having mentioned the facilities in one of his books.

“You don’t have to put them in a detention center. Bill, you’re the first one to mention a detention center,” Trump said on The O’Reilly Factor after host Bill O’Reilly brought up the immigrant detention system, which, according to the American Civil Liberties Union, “locks up hundreds of thousands of immigrants unnecessarily every year, exposing detainees to brutal and inhumane conditions of confinement at massive costs to American taxpayers.”

“OK, so you wouldn’t do that. You would keep them in their homes,” O’Reilly said.

“No, I never said—I’ve never even heard the term,” Trump said. “I’m not going to put them in a detention center.”

O’Reilly pointed out that Trump had said he would model his immigration proposal after President Dwight D. Eisenhower’s 1954 program “Operation Wetback,” which used detention centers. The policy “plucked Mexican laborers from fields and ranches in targeted raids, bused them to detention centers along the border, and ultimately sent many of them deep into the interior of Mexico, some by airlift, others on cargo boats that typically hauled bananas,” according to CNN.

“No I said it, yeah, I said that is something that has been done in a very strong manner,” Trump interjected. “I don’t agree with that, I’m not talking about detention centers.”

Trump’s 2011 book, Time To Get Tough, referred to immigrant detention centers, as Fusion reported. The book used the term “immigrant detention facilities” and laments that undocumented immigrants at some detention centers may have access to “resort-like accommodations” like a vegetable bar and immigration attorneys.

The immigration proposal posted to Trump’s website calls for a “Detention—not catch-and-release” policy on immigration. “Illegal aliens apprehended crossing the border must be detained until they are sent home, no more catch-and-release,” reads the candidate’s website.

Democratic Party nominee Hillary Clinton’s immigration plan calls to “end family detention for parents and children who arrive at our border in desperate situations and close private immigrant detention centers,” but does not call for the complete end to the immigrant detention system.

Rewire Immigration Fellow Tina Vasquez has reported that Clinton’s plan would instead leave detention up to the government instead of private facilities:

Put plainly, Clinton’s plan is to stop the privatization of detention centers and instead, make them a function solely of the government. In October, Clinton’s campaign spokeswoman Xochitl Hinojosa released a statement on Clinton’s behalf further outlining her plan, saying Clinton “believes that we should not contract out this core responsibility of the federal government, and when we’re dealing with a mass incarceration crisis, we don’t need private industry incentives that may contribute—or have the appearance of contributing—to over-incarceration.”