BOGOTA, Colombia -- 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.

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.

Get Breaking News Delivered to Your Inbox

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.