WATERVILLE — A carnival ride that malfunctioned and injured three children Friday will remain closed until an investigation is completed by the state fire marshal. Mary Robinson, the office manager for Smokey’s Greater Shows, said Saturday that the Dragon Wagon, a small roller coaster-type ride, will be closed at the fair until further notice, but other rides are open. The festival, a fundraiser for Waterville-based Maine Children’s Home for Little Wanderers, started on Thursday and is scheduled to go through Sunday at the Head of Falls park in Waterville.