The girls were on foot and trying to cross the northbound side of Route 3 near Waugh Chapel Road in Gambrills, north of Crofton.
A car hit one of the girls, age 15, and stopped to check on her, according to police who arrived at the scene. Another vehicle slammed into the back of the stopped car, hurting a passenger of that vehicle and continuing a chain reaction that injured several others.
In all, four vehicles and two pedestrians were involved in the accident. Seven people were taken to area hospitals while another person at the scene refused medical treatment.
A 30-year-old man, the driver of one of the vehicles, was rushed by helicopter to the Prince George's Trauma Center with serious injuries. The 15-year-old pedestrian who was hit in the initial accident was taken to John Hopkins Children's Center, also with serious injuries. The others sustained less serious injuries and were transported to Baltimore Washington Medical Center.
Anne Arundel County police are still investigating the initial cause of the crash.