WELEETKA — A fatal oil tank explosion last week was caused by a man opening a hatch on the tank while smoking a cigarette, an Okfuskee County undersheriff said Thursday.Zachary Pangle, 21, of Weleetka, died in a Tulsa hospital’s burn unit two days after the April 14 explosion from what the state medical examiner described as "thermal injuries.”"Mr.Read more on NewsOK.com