As at least three major wildfires continue to force evacuations in the southwestern state of Arizona, a U.S. Senator is defending comments he made blaming illegal immigrants for some of the blazes.

Senator John McCain said on Saturday there was substantial evidence that the fires were started by people who illegally crossed into Arizona from Mexico. He made his comments while touring damage from the Wallow Fire – Arizona's largest ever wildfire.

Many immigrants rights supporters criticized McCain for not providing proof to support his claim. But McCain said on Monday that he had seen evidence to back the claim, although he did not mention anything specifically. Investigators have not blamed the fires specifically on illegal immigrants.

Arizona was at the center of the illegal immigration debate after passing a measure last year that would have allowed police officers to check the immigration status of anyone suspected of being in the U.S. illegally.

The Wallow Fire has so far burned over 207,000 hectares and is only 51 percent contained. As many as 10,000 people have been displaced by fires across the state.