(WBIR- Rutherford County) Murfreesboro police made the largest heroin bust ever in department history and one of the largest in the state.

Officials announced details Tuesday afternoon of the bust made Jan. 23.

Special investigators and TBI agents arrested two Colorado women for trafficking.

Police stopped Elizabeth Castillo and Rosalinda Vallejo on Saturday and allegedly found more than five kilograms of powdered heroin.

Officials with the Knox County District Attorney General's office determined this amount of heroin is valued at more than $1 million for about 50,000 doses.

Heroin use and deaths related to heroin overdoses have been on the rise in Tennessee. Police said the biggest concern is the unknowns of the drug.

“Heroin is such a very dangerous, dangerous drug,” said Kyle Evans with Murfreesboro police. “It can be laced with other drugs, which causes deaths during overdoses. You just don’t know what it’s being laced with. It’s also associated with other opiate-related drugs people have been using for many year. They’ll switch to a cheaper form of heroin. Again, it’s a cheaper form of opiates.”

Police have also linked the spike in heroin use to the crackdown on prescription drug abuse.

The Knox County District Attorney General's office is part of statewide efforts to keep heroin off the streets.

The office has prosecuted cases with individuals who have dealt in kilo amounts, but Sean McDermott, assistant district attorney, said they have never been able to grab all of that at one time.

"Getting five kilos off the street is a significant dent in the heroin flow coming from source cities to Tennessee," McDermott said.

Officials with the district attorney's office said heroin is not regulated like prescription pain pills. If addicts turn to heroin usage as a cheaper alternative, it is risky because a user never knows what could be laced into the heroin.

"Simply put, heroin is probably the most dangerous drug that we're dealing with on the street levels so we have to fight it aggressively," said deputy district attorney general Kyle Hixson.

The Knox County District Attorney General's office was not involved in the Murfreesboro investigation, but it is not uncommon for the different agencies and offices to share information and tips about the drug pipeline.

WSMV contributed to this report.