Two 15-year-old girls from Merrimack were last seen hitchhiking in the summer of 1973 before their bodies were found months later. Decades later, the case remains unsolved.Last seen alive: July 12, 1973Bodies found: Sept. 29, 1973City/town: CandiaCase status: Unsolved homicideDiane Compagna and Anne Psaradelis had been seen at Hampton Beach and were last seen hitchhiking in the direction of Merrimack late in the afternoon of July 12, 1973.It was initially thought that the girls had run away, but their bodies were found on Sept. 29, 1973, in a wooded area off of New Boston Road in Candia — a short distance away from Route 101, a common route used by drivers in the Merrimack Valley to travel to and from Hampton Beach.The manner of girls' deaths was undetermined because of the condition of their bodies, but it is believed that the girls were strangled to death, authorities said. Some investigators at the time believed there might have been two killers.During what initially was a missing persons investigation, police at the time learned that one of the girls told some people that she had been sexually assaulted on July 4, 1973, eight days before she disappeared. A potential suspect was questioned about the alleged sexual assault after the girls vanished, but he was not arrested.Despite decades of investigating, the cases have remained unsolved. Can you help police solve this case? Submit a tip to the New Hampshire Cold Case Unit.