BREVARD COUNTY, Fla. -- Investigators in Brevard County are trying to find a paramedic accused of stealing morphine out of a vial. Someone replaced the morphine with an unknown substance and now people are being drug tested to find out who did it.

It's down to about 16 Brevard County Fire-Rescue personnel who would have had access to the drugs inside their ambulance. Last month, a senior medic working the ambulance at Brevard County's station 60 noticed the cap to a vial of morphine appeared to be "sticking up" and notified the chain of command.

The vial, they determined, had been tampered with, the morphine removed, another substance poured in and the cap somehow glued back in place. The fire department notified the Drug Enforcement Agency and the sheriff's office.

"We are looking at multiple persons of interest. There are no named suspects right now," said Agent James Core, Brevard County Sheriff's Office.

Fire-rescue administrators said they have traced the vial back to its arrival and identified all personnel who might have had access to it. The drugs are kept under lock and key, but the keys are handed off from shift to shift.

"They do have safeguards, so it is not in the open and it is somewhat guarded," Core said.

Fire rescue personnel said they believe the morphine was replaced with a saline solution, which normally might not harm a patient but it would also not provide the pain relief a patient and the person treating them would expect.

"That element has definitely come into play, absolutely it is a concern," Core said.

The fire department has drug tested several employees who had access to the morphine, but experts said it can be difficult to find traces of the drug once 48 hours has passed.

The county was allowed to park its ambulance for free inside the Cape Canaveral fire station, but the investigation solely revolves around county personnel who have been assigned to the station, not the city firefighters.