At least four people died and 17 others went missing on Wednesday after three boats sunk in a reservoir in Bajaur district of Pakistan's northwest Khyber Pakhtunkhwa province, local media reported.According to the reports, a boat with 18 people on board sunk in Raghagan Dam in the district when it went to deep water on a recreational trip, the Xinhua news agency reported.Shortly after the accident, two rescue boats with seven personnel on board also sunk in the reservoir when they rushed to rescue the drowning tourists, the reports added.Another group of rescuers started rescue operation and rescued four persons and took out four bodies from the reservoir.The bodies and other four rescued persons have been shifted to a hospital.The rescue team told media that they were searching for the missing people, adding that there was almost no chance of their survival.The reports quoting local police said that the first boat sunk due to overloading and the rescue boats faced the accident because the staff were not experienced and they failed to control the boats.