The former commander of an elite wildland firefighting team has pleaded guilty to starting a fire in a national forest, though he said he doesn't know why he did it.

Van Bateman, 55, told U.S. District Judge Paul Rosenblatt on Monday that he started the 2004 fire in the Coconino National Forest and left despite knowing the blaze would grow. The fire near Flagstaff burned about 21 acres.

"The line between a good fireman and an arsonist is a fine line. I did not do this for profit or gain. I am happily married. I have no idea why I started these two fires," Bateman wrote in his confession.

Bateman was the head of a wildfire management crew that is called in for the biggest and most severe wildfires, and helped suppress the largest wildfire in Arizona history. That blaze was started by a part-time firefighter.

There was no answer at Bateman's home phone Tuesday, and his lawyer Grant Woods did not immediately return a call seeking comment.

Bateman, a 34-year veteran of the U.S. Forest Service, signed two statements last year, one denying that he set any fires "that were not prescribed, authorized, or controlled burns on Forest Service land." The second, signed later the same morning, said he lit two fires.

Bateman, who had been accused of setting another, much smaller fire, could get up to five years in prison and be fined up to $250,000 at sentencing Jan. 22 for his conviction on setting timber afire. Prosecutors agreed to drop another such charge and two counts of arson.

"Bateman joins a small universe of firefighters who, for reasons we may never fully understand, violated the public's trust by igniting fires, not extinguishing them," U.S. Attorney Paul Charlton said in a news release.