Four crew members who went missing after a police helicopter crashed into a reservoir in a northern suburb of Beijing on Wednesday have all died, police said Friday. Two bodies of the crew members were retrieved from the reservoir late Wednesday and two others were found on Thursday, the Beijing police said in a statement. Altogether five crew members were aboard the helicopter that was returning from a search-and-rescue drill over the mountainous region of Miyun County. A crew member was rescued from the water shortly after the crash. The Beijing water and environmental authorities have launched an emergency plan to ensure the safety of the water as the reservoir is a major drinking water source for Beijing residents. On July 16, the Beijing Municipal Public Security Bureau set up a police aviation fleet to enhance its emergency-response capability. There were four helicopters in the fleet before the accident occurred, and Beijing police said it is considering the purchase of another six helicopters over next five years.