Narcotics

You are sent to a motel room to conduct an investigation.  There you find a deceased 30-year-old Hispanic male lying between two queen-sized beds.  His suitcase has bag tags from a local international airport.  His route was Cuba to Ontario, then Ontario to Newark, NJ.  Upon looking into his suitcase you notice an area where something large, half the size of the case is missing.  Based upon past experience you conclude he was a drug mule.  He was likely recruited to transport a large number of drugs from overseas into the U.S.
You also know that many of these transactions end with the mule being murdered, drugs were stolen, and promised money never delivered.  You find what appears to be a single needle mark, but no others on the deceased.  Upon questioning the motel clerk he states the man checked in about 6 pm and a woman came to the room alone at about 2 am and left by 3 am.
The local police want this case to be classified as an overdose if toxicology supports that finding.  You as a narcotics agent believe it to be a homicide.  The local police understand your position, however, they and the mayor do not want a lot of unsolvable homicides in the town.
How do you handle this situation?
You also know they are correct, that this case will likely never be solved.  Plus the mayor is a very powerful man who will likely find a way to punish you if you push for a homicide investigation.
What do you do?
Why did you make the choices you made?
How could your determination affect the victim? Victim’s family?  Community as a whole? Your own career?