The Maine Drug Enforcement Agency on Friday arrested a 40-year-old man from Sanford on aggravated drug trafficking charges as he returned from Lawrence, Massachusetts, with a large quantity of heroin and cocaine, police say.

Drug agents and Wells police stopped a car in which Shane Eisener was the passenger, and found 42 grams of heroin/fentanyl mix and 15 grams of cocaine in his possession. He was charged with aggravated trafficking of scheduled drugs, and is due to be arraigned Monday.

The estimated street value of the drugs is roughly $7,800. The driver of the car was not charged, but the state Attorney General’s Office is reviewing the case and the driver may be charged later.

Eisener is being held without bail at the York County Jail in Alfred because he was already out on bail on another charge when he was arrested Friday.

Additional arrests of Eisener’s associates are expected. MDEA Cmdr. Scott Pelletier said investigators are looking into whether Eisener had any connection to the half-dozen people in Sanford who overdosed on opiates during a 24-hour period June 24-25.