AUBURN, Ind. (AP) — A coroner in northeastern Indiana says he doesn't know whether a 31-year-old volunteer firefighter's work to put out a house fire in hot temperatures caused his fatal heart attack.

An autopsy confirmed that Travis Miller suffered a heart attack, but DeKalb County coroner Jeff Warner tells The Journal Gazette of Fort Wayne (http://bit.ly/p9TJaO ) it didn't link the attack to the heat, overexertion, a health condition or some combination of those factors.

Miller responded with members of the Waterloo-Grant Township Fire Department to assist the Butler Fire Department in that town the evening of July 19 when it was about 90 degrees.

Officials say Miller arrived home about 10:30 p.m. and went to bed. Emergency crews were called about six hours and found him dead.