A months-long investigation has resulted in the arrests of six Maine residents and a Connecticut man who allegedly smuggled Suboxone strips hidden inside holiday greeting cards into the Maine State Prison.

The alleged kingpin of the operation was 71-year-old Douglas Mazzotta of Middletown, Connecticut, who has been charged with drug trafficking and illegal importation of a Schedule W drugs. Mazzotta mailed the strips, which were purchased in Connecticut, to the prison under the direction of an inmate, 41-year-old Paul Milardo of Cushing, who is serving a robbery sentence. The Suboxone strips were purchased in Connecticut for $5 each and sold at the prison for about $400 each.

Drug agents began their investigation last September and discovered “a complex Suboxone trafficking organization (at) the Maine State Prison in Warren,” according to a press release issued Wednesday by Commander Scott J. Pelletier of the Maine Drug Enforcement Agency.

Pelletier said investigators determined that the Suboxone was shipped from Connecticut to a number of addresses in midcoast and central Maine. Suboxone is prescription medication used to treat opiate addiction. It is often sold and traded by people who abuse opiates.

During their investigation, agents and inspectors for the U.S. Postal Service intercepted two shipments containing 80 Suboxone strips that were mailed to addresses in midcoast Maine.

Pelletier said strips were concealed inside greeting cards and smuggled into the prison during prisoner visits. Once the strips were inside the prison, Milardo arranged to have several inmates sell them to other prisoners. Customers paid Milardo by having outside people transfer money orders to personal accounts or prisoner accounts, Pelletier said. Prison commissary items were also traded for the drug.

It was unclear from the press release how Milardo paid Mazzotta.

Mazzotta was arrested by an FBI task force on Jan. 13 in Connecticut on Maine warrants. He is being held at the Hartford House of Corrections in Hartford, Connecticut. He has agreed to waive extradition and will be brought to Maine this week.

Milardo has been charged with two counts of aggravated trafficking in Schedule W drugs and remains in custody at the state prison. Another inmate, 30-year-old Matthew Binnette, has been charged with trafficking in Schedule W drugs.

Also arrested and facing charges are:

• Christy Nason, 38, of Warren, charged with trafficking in Schedule W drugs. She is being held at the Knox County Jail.

• Edward Robinson, 33, of Randolph, charged with trafficking in Schedule W drugs. Robinson is being held at the Knox County Jail.

• Lisa Work, 27 of Topsham, summonsed for conspiracy to traffic Schedule W drugs and released.

• Travis Work, 30, of Topsham, charged with trafficking in Schedule W drugs. He is in the custody of the federal bureau of prisons on an unrelated charge.

The Maine Drug Enforcement Agency and prison investigators were assisted by U.S. postal inspectors, the Sagadahoc, Knox and Lincoln County Sheriff’s Office, and Maine State police.