The State Fire Marshall’s Office is trying to determine what caused a fire in a mobile home that killed two men in Bonnie Tuesday morning.   Jefferson County Coroner Eddie Joe Marks indicated the fire was at a trailer at 13853 East Davis Road, south of Mount Vernon.  The owner and victim, 72-year old Gary Melton and his brother, 73-year old Don Melton, were both pronounced dead at 2:54 AM.  The fire was reported around 1:24 AM Tuesday.  Illinois State Police are assisting the Illinois State Fire Marshall’s office and the Jefferson County Sheriff’s Office in the investigation.  No foul play is suspected at this time.