With more than half a dozen wildfires currently burning throughout Arizona and investigators trying to track down their cause, Arizona Sen. John McCain says illegal immigrants may be to blame in some cases.

"We are concerned about, particularly with areas down on the border, where there is substantial evidence that some of these fires were caused by people who have crossed our border illegally," the Republican senator said after a tour Saturday of an area affected by the so-called Wallow Fire.

In a press conference that followed, McCain said border-crossers have set fires "because they want to signal others. They set fires to keep warm and they have set fires in order to divert law enforcement agents and agencies from them. The answer to that part of the problem is to get a secure border."

On Monday, the senator's spokeswoman said McCain's comments were not in reference Wallow Fire, but instead to smaller ones that have popped up along the border, particularly in the Coronado National Forest area.

McCain also issued a statement Monday saying that he got his information directly from a senior Forest Service official, who told him, "Some wildfires in Arizona (across our southern border) are regrettably caused by drug smugglers and illegal immigrants.

"This statement is consistent with what we've been hearing for years, as well as testimony by the Forest Service and media reports dating back as far as 2006," McCain said.

The Wallow Fire is the largest in Arizona's history, burning more than 519,000 acres -- more than 800 square miles -- in about three weeks. Its cause is still under investigation.

This is not the first time fingers have been pointed at illegal immigrants when it comes to the cause of wildfires. Jim Upchurch, the Coronado National Forest supervisor, told the Arizona Daily Star newspaper earlier this month that some fires are ignited by smugglers or illegal immigrants. Fires are also caused by ricocheting bullets, campfires and welding equipment.

Last summer McCain and Sens. Jon Kyl, R-Ariz., Lisa Murkowski, R-Alaska, and John Barrasso, R-Wy., asked the Government Accountability Office to investigate fires that may have been caused by illegal immigrants within 100 miles of Arizona's border with Mexico.

The results of that study are scheduled to be released later this year and will highlight wildfires over the last five years that have been attributed to undocumented residents.

McCain said Monday he finds it unfortunate that some, whom he would not name, would try to politicize the fire for political gain.

"While Arizonans continue to face the enormous challenges related to these wildfires, it's unfortunate that some are inserting their political agenda into this tragedy," he said.