Interviewed on ABC's "Good Morning America," Tuesday, McCain said he's "not sure what all this controversy is about," and that his remarks were based on a briefing he received from a Forest Service official.
"Sheriff Larry Dever will tell you that the Monument Fire was started when the park, the forest was closed. So anyone who was in there is illegal," McCain said.
The Forest Service has only said the wildfires appear to be "human caused" but has not offered any evidence the suspects may have been illegal immigrants.
"The fact is that as far back as 2006 the Forest Service testified before Congress, and I quote, 'Large numbers of warming and cooking fires built and abandoned by cross border violators have caused wildfires that have destroyed valuable natural and cultural resources,'" McCain said.
Critics say McCain's claims only add fuel to an ongoing political debate.
"The sad thing is that the intention was pretty clear," Clarissa Martinez with the National Council of La Raza said. "It was to demonize immigrants and demonize Latinos."