Yellow pills blamed for killing at least five people and hospitalizing dozens more contained a "highly dangerous" combination of two synthetic opioids never before seen in Georgia.

According to an analysis by the Georgia Bureau of Investigation’s crime lab, the two chemicals in the pills stamped “Percocet” are  chemically similar to fentanyl.

“It is unknown how the human body will react to this drug since it is not intended for human or veterinary use,” the GBI said in a statement.

Cyclopropyl fentanyl, one of the compounds, has “not previously been seen in Georgia" and the “U-47700 is a synthetic opioid 7.5 times stronger than morphine. “

The GBI warned that the pills should not be handled because the drugs could be inhaled or absorbed through the skin and “are extremely toxic in even the smallest quantities.”

Katherine Mattox said her brother, Gregory Mitchell, was an Army veteran.

The GBI released the results of additional testing Tuesday evening, a little more than a week after the first of suspected overdoses in Middle Georgia began showing up at local hospitals.

The tested pills -- sold on the street -- were recovered by Macon-Bibb County law enforcement after a cluster of suspected overdoses mostly in Middle Georgia -- in Bibb, Houston and Monroe Counties but also in the Albany area. It was identified more than a week ago when the Georgia Poison Control Center started getting calls late on Sunday, June 4.

At least five people have died -- three in Macon and one each in Houston and Monroe Counties.

Officials can’t say for certain if the pseudo Percocet is to blame until the state completes testing on blood and urine samples taken in the cases of those who died and who were hospitalized.

Macon-Bibb County Chief Coroner Leon Jones said the cluster of suspected overdoses in Houston, Bibb, Monroe and Dougherty Counties is “about as close to an epidemic as you can get. We’ve never seen anything like this.”