A 12-year-old Anacostia girl was arrested on a street near her home last night and charged with selling heroin in the company of a man police described as "a friend of the family."

Police undercover narcotics officers who arrested the pair about 7:30 p.m. in the 2400 block of Martin Luther King Avenue SE said they found 15 small packets of heroin in a nylon backpack the girl was wearing. They estimated the street value of the heroin at $600.

Narcotics branch detective Charlie Beard said the arrests were made after officers witnessed several suspected narcotics transactions involving the suspects. Beard said the girl apparently carried the heroin in the backpack while her adult companion arranged sales with customers who approached on the street. Once a transaction was made, Beard said, the girl would pass the heroin to to the man, who then gave it to the buyer.

Police said the girl lives with her mother near the site of the arrest and is believed to be in the sixth grade at a Southeast elementary school. She was being held last night at the juvenile receiving home pending a hearing today in juvenile court where she will face charges of possession of heroin and possession of heroin with intent to distribute.

An adult suspect arrested at the scene on the same charges was identified as Ralph E. McGruder, 34, of 2641 Barney Pl. SE. Police said he was being held on bond last night in the central cellblock pending arraignment today in D.C. Superior Court. A second man, who police allege bought heroin from the suspects, also was being held last night.

Beard, who said he and other officers were patrolling King Avenue last night because of evidence of increased drug trafficking there, described himself as "very startled," to find a 12-year-old involved.

"It's not unusual to find kids as young as 15 and 16 doing this kind of thing," Beard said, "but I was not prepared for this."

Beard said the girl, who apparently had never used drugs herself, told investigators she expected to be paid for her role in the affair, but that she didn't know how much.

"She's an average 12-year-old child. She's a child," Beard said. "Somebody, a person with no conscience, is just using a child."