Pills that caused eight overdoses in Central Georgia in the past week contain a synthetic version of the painkiller fentanyl, the GBI says.

On Friday, the GBI released a statement on the fake Percocet pills blamed for overdoses in Warner Robins and Bibb County in the past week.

They said those pills are similar to the batch that caused dozens of overdoses, and at least two deaths, in Central Georgia in June.

Both batches contain cyclopropyl fentanyl.

That's the substance first identified by the GBI during the June investigation.

The June batch also contained another synthetic opioid, U-47700. In June, the GBI said that substance was 7.5 times stronger than morphine.

On Friday, GBI spokeswoman Nelly Miles says the latest batch also contains U-47700, but possibly not as much.

She would not comment on why the latest batch does not appear to be as potent.

She said, "We really just appreciate getting the word out, and this really just underscores the dangers of counterfeit drugs."

The GBI says both substances -- cyclopropyl fentanyl and U-47700 -- are highly dangerous, even in small quantities, and could be absorbed through the skin.

On Thursday, Warner Robins police Chief Brett Evans said they're still looking for the source of the fake Percocet pills.

He said no new overdose cases had been reported since Tuesday.

Anybody with information on the case can call Warner Robins police at (478) 302-5380 or Macon Regional Crimestoppers at 877-68-CRIME.