One of the riders has sustained serious injuries and was taken to hospital for treatment. Police Constable Kristian Budden, of the Roads Policing Team, said: "An investigation is under way into the circumstances of this incident. "I am appealing to anyone who may have seen what happened or was in the area at the time and may have seen a moped or scooter to please get in touch." Anyone with information is asked to contact Dorset Police online or by calling, quoting incident number 55260120501. Alternatively, independent charity Crimestoppers can be contacted anonymously online using its website or by calling Freephone 0800 555 111.