Local and state police raided a Biddeford apartment Tuesday afternoon, charging two people from Boston and two from Biddeford with trafficking in crack cocaine. Officials seized $10,000 in drugs and a loaded pistol.

The arrests were the result of a monthlong investigation that began when neighbors of 47 Summer St. told police that there had been an unusual amount of activity at the building, including cars with out-of-state license plates dropping off and picking up people.

The Maine Drug Enforcement Agency made undercover purchases of drugs, which enabled them to get a search warrant. Biddeford police, the Southern Maine Violent Crimes Task Force and MDEA raided the building at 2 p.m. Tuesday, seizing 3 ounces of crack cocaine, 8 grams of heroin, scales and packaging material, $800 and two electronic benefit transfer cards, sometimes used by welfare recipients as collateral for drugs, police said.

Police arrested Christopher Clayton, 24, and Jasmine Branao, 23, of Boston, on charges of aggravated trafficking in crack cocaine; and Athina Goldthwait, 32, and Casey Goldthwait, 24, both of 47 Summer St., with trafficking in crack cocaine.

Police say that out-of-state drug traffickers were allowed to stay in a back bedroom of Apartment 8 at the address, where they divided up wholesale quantities of the drugs for retail sales, and the drugs were then sold from Apartment 1.

All four people arrested are being held at York County Jail in Alfred, Clayton on $75,000 bail, Branao on $50,000 and Athina Goldthwait on $30,000. Casey Goldthwait is being held without bail because she was already out on bail for a pending drug charge.