DORCHESTER – State Police arrested three men and confiscated three duct-taped bricks of fentanyl following a six-month investigation into opioid trafficking.

Pablo Alberto Arias Herrera, 48, of Dorchester, and Omar Medina-Santiago, 31, and Julio Missael Ramirez Peguero, 26, both of Roslindale, are scheduled to be arraigned in Dorchester District Court on Monday. Each was charged with trafficking in a Class A substance and conspiracy to violate drug laws, Massachusetts State Police said.

During the arrest, investigators confiscated fentanyl bricks wrapped in duct tape which weighed more than three kilograms. The drug is a synthetic opioid that is 80 to 100 times more powerful than morphine, police said.

The arrest culminates an investigation targeting a fentanyl trafficking organization operating around Boston. It began late 2018 and was conducted by troopers assigned to the Suffolk State Police Dtective Unit and members of the federal Homeland Security Investigations Boston Strike Force, police said.

“The investigation established that three suspects would be in possession of three kilograms of fentanyl on Friday,” police said. The men were arrested at South Bay Plaza in Dorchester and detectives found the drugs in a backpack, police said.

Each suspect also had outstanding warrants for narcotics offenses. They were held in custody over the weekend, police said.