At least two dozen people were arrested on drug charges in a sting operation that uncovered evidence of drug sales at Fort Leonard Wood, authorities said.

Some civilian employees of mess halls at the U.S. Army fort were among those arrested Wednesday, Pulaski County Sheriff J.B. King said. No military personnel were believed to have been arrested, he said.

During the two-year investigation, an undercover state trooper purchased heroin, crack cocaine, marijuana, methamphetamine and ecstasy, authorities said. During Wednesday’s arrests, officers also found what was believed to be a live hand grenade and one other military explosive device, as well as firearms, in the suspects’ arsenal.

King said about 20 suspects were arrested in Pulaski County and six or seven others in surrounding counties. The total number of people being sought was not disclosed.

Most of the state charges were for felony drug possession or drug distribution, carrying penalties of up to 15 years. Details on federal warrants involving allegations of drug sales at the fort itself were not available because the warrants have been sealed, King said.