All 17 people aboard a military helicopter that crashed in a mountainous area over the weekend were found dead when searchers reached the site in western Colombia, the army said Monday.The statement said the accident occurred Sunday afternoon in a rural zone of Pensilvania province northeast of the capital, Bogota. The dead included the aircraft`s five crew members and 12 soldiers, reports abcnews.The army said it appeared that reduced visibility from bad weather may have been a factor in the crash, but added that investigators had not yet made a finding.Authorities said the troops killed were involved an operation against guerrillas of the National Liberation Army, which is the second largest rebel movement involved in the country`s five-decade civil conflict. The main movement, the Revolutionary Armed Forces of Colombia, is in negotiations with the government that are believed close to producing a formal peace accord.