(CNN) -- Pittsburgh police Wednesday had six "persons of interest" in custody in connection with the shooting of three students near their high school, authorities said.
One student was grazed in the head, another was struck in the neck and shoulder, and a third was hit in the leg and foot, according to Pittsburgh police spokeswoman Diane Richards.
Richards said the six people being questioned were picked up at a house near the school. She said the shooting may be drug-related.
"We don't know if there were multiple shooters at this time," Richards said. "No one is talking at this time."
One of the victims was listed in stable condition at Allegheny General Hospital, according to a hospital spokeswoman. Authorities said the injuries were not life-threatening.
The shots rang out near Brashear High School shortly after the last bell rang at 2:46 p.m., said Ebony Pugh, a spokeswoman for Pittsburgh's public schools. There is a middle school adjacent to the high school.
The students were approached by at least one gunman who came out of the woods and opened fire, the school spokeswoman said. They were shot while walking to their cars.
At least two of the victims managed to run back into the school and notify authorities. The identities of the victims, in their mid- to late teens, were unknown.
Richards said the shooting may have been in "retaliation" for an earlier incident but did not elaborate.
CNN's Lawrence Crook contributed to this report.