ROCKLAND — Four Knox County residents were arrested on various drug charges over the past week by area police and the Maine Drug Enforcement Agency.

All four were on probation for prior convictions at the time of their arrests, and are being held in the Knox County Jail. The latest charges involve the sale of cocaine and heroin.

Supervisor James Pease from MDEA’s midcoast task force, said those arrested are:

Charles Harris, 43, of Rockland, aggravated trafficking in cocaine and Suboxone, violation of probation and possession of hydrocodone. This charge was aggravated due to the act taking place in a drug-free zone.

Amy Ashley, 30, of Rockland, for trafficking in cocaine and violation of probation.

Jaclyn Erickson, 24, of Rockland, for aggravated trafficking in cocaine, violation of bail and violation of probation. This charge was aggravated due to a prior drug trafficking conviction.

Jeremy Yeaton, 27 of Thomaston, for aggravated trafficking in heroin and violation of probation. This charge was aggravated due to a prior drug conviction.

At the time of her arrest, Erickson was out on bail on a charge of trafficking in prison contraband for a 2008 arrest. She is on probation for a 2007 arrest for trafficking heroin. Yeaton was also on probation for a previous drug charge. Harris’ and Ashley’s probations were not related to drug charges.

Pease said the Ashley and Erickson arrests were related, but the Harris and Yeaton arrests were not connected to the others.

The arrests were the result of an ongoing investigation. Assisting the MDEA in the arrests were Thomaston and Rockland Police departments and the Knox County Sheriff’s Department.