On 14 January 2014, the experienced pilot of an EC 135 HEMS aircraft lost control as a result of a collision with unseen and difficult to visually detect power lines as it neared the site of a road accident at Sollihøgda to which it was responding which damaged the main rotor and led to it falling rapidly from about 80 feet agl. The helicopter was destroyed by the impact which killed two of the three occupants and seriously injured the third. The Investigation identified opportunities to improve both obstacle documentation / pilot proactive obstacle awareness and on site emergency communications.