Gang members and four corrections employees are facing federal charges in connection with wide-ranging criminal schemes over the last decade to smuggle drugs into Virginia prisons and commit robberies, prosecutors announced Friday.

Members of the New York City-based Mad Stone Bloods (MSB) brought cocaine, heroin, cellphones and other contraband into three Virginia penitentiaries with the help of three guards and a counselor, and even maintained a sexual relationship with one, according to an indictment.

In all, 20 people from Virginia and New York were charged in the conspiracies, which played out in part at the Greensville, Lawrenceville and Buckingham correctional centers in southern Virginia, according to the indictment.

The case in U.S. District Court in western Virginia is the third major prosecution in recent years involving allegations of drug smuggling against inmates and guards at prisons in the Mid-Atlantic region.

Last month, more than 50 inmates and guards were charged with bribery and drug conspiracy inside Maryland’s largest prison.

In 2013, more than two dozen correctional officers in Baltimore were indicted on a charge of helping members of a major national gang, the Black Guerrilla Family, operate a drug-trafficking and money-laundering scheme inside a detention center. The investigation uncovered a gang leader had impregnated four guards.

In the Virginia case, federal authorities said that in 2011 and 2012, an unnamed correctional officer, who worked at the Greensville and Lawrenceville facilities, engaged in a sexual relationship with a leader of the MSB.

The guard used her position to smuggle drugs into the prisons and distribute them to multiple gang leaders, according to the indictment. MSB leaders paid her for bringing the controlled substances into the facilities.

In September, two correctional officers who were also members of MSB, conspired with an inmate and MSB member who was at the Buckingham facility to develop a plan to obtain drugs from other MSB gang members outside the prison, according to the indictment.

The guards met a gang member in Petersburg, Va. and bought crack, powder cocaine and marijuana to distribute at the prisons, according to the indictment. The pair were arrested shortly after the buy.

The guards were identified as 20-year-old Shaunda Rochelle Jones, who went by the name Lady Stone in the MSB, and 20-year-old Jaymese Jenee Jones, who had the nickname Precious Stone. Both live in Farmville, Va.

Six members of MSB in Virginia, some top leaders among them, were charged with racketeering. They include Michael Demont Dove, also known as “Ducatti Black”; Terrance Nathaniel Brown, or “War”; and Corey Owens, also known as “Mr. Hardhead.”

As of Friday afternoon, attorneys were not listed in court papers for those alleged gang members or the charged guards.

The indictment alleges members of the MSB gang have carried out armed robberies, drug dealing and various killings to maintain their criminal operation in Virginia. MSB operates across the Eastern half of the United States from Texas to Connecticut.