Boston police arrested two men from Martha’s Vineyard Monday on drug trafficking charges, part of an ongoing drug investigation.

According to a press release from Boston police, members of a District B-3 (Mattapan) Neighborhood Drug Control Unit arrested Peter Estrella, 30, and Adam Robinson, 35, both of Vineyard Haven, after witnessing what they said appeared to be a drug transaction near Kingbird Road in Mattapan.

Police said they observed a pickup truck from the Vineyard arrive and park in the area, and a short time later a red vehicle pulled up behind the truck and a male passenger walked from the pick-up truck to the other vehicle, exiting about 10 minutes later. The pickup truck then left the area, police said, and officers continued surveillance of both vehicles before conducting a traffic stop of the pickup truck.

Officers said they found 168 paper folds of heroin, or about 30 grams, a plastic bag with 14 grams of cocaine, nine Xanax pills and two Trazadone pills. Mr. Robinson and Mr. Estrella were placed under arrest on charges of trafficking class A drugs (heroin), possession with intent to distribute class B drugs (cocaine), class C, and class E drugs, and conspiracy to violate drug laws.

Police said the driver of the other vehicle was identified as a 41-year-old Everett man, Bernard Medero. After taking Mr. Medero into custody and executing a search warrant at a residence, Mr. Medero was charged with several drug-related offenses, according to police, as well as unlawful possession of a firearm.