Last year police charged a guard and two others after seizing marijuana, oxycodone pills and methamphetamine that was to be sold in the Peace River Correctional Centre.
On Wednesday RCMP charged former inmate William Blackwood and two others with conspiracy to traffic meth and pot.
Trafficking charges laid last year against Thomas Black, a correctional officer at the facility, are still before the courts.
The others charged in the case include Chantelle McAllister, Robin Wachter, Farrah Hachey, and Shauna Cunningham.
Police allege people inside and outside the jail conspired to sell drugs to inmates.
Sgt. Jason Gibson said it is pretty rare for a guard to face such charges.
"We are not blind to the fact that hard drugs are going into our institutions," Gibson said Wednesday.
"I have been doing drug and organized crime work for awhile and it is certainly the first one where me or any of the people in my unit have investigated something like this."
Gibson declined to identify the organized crime group or gang involved in the case.
The Peace River Correctional Centre is a provincial jail that houses about 300 male inmates.