The highway robbers looted a passenger coach and deprived the passengers of all their cash, valuables and mobile phones.According to details, the robbers boarded a coach heading to Karachi from Quetta at Mastung. They started looting passengers and deprived them of their cash, cell phones and other costly items till their journey up to Kalat.Later, the passengers protested at Singdas along RCD Highway. They also tried to block the highway but police foiled their bid.Police rounded up driver and cleaner of coach for interrogation.