( CNN ) -- A Black Hawk helicopter crashed Thursday in southern Afghanistan , likely killing all four of its crew members -- all of them Americans -- a U.S. military official said . The crash occurred in bad weather , though the official said , `` We can not yet rule out enemy action . '' Troops at a combat outpost in the area waiting to be picked up saw the crash happen , the official said . Another helicopter flying nearby was not affected . Fatal helicopter crashes involving members of the NATO-led International Security Assistance Force are not unprecedented in Afghanistan , with some of the aircraft brought down by enemy fire while others crashed for mechanical reasons . The single deadliest loss for U.S. troops since the Afghan war began in late 2001 happened in August , when 30 U.S. service members died when a helicopter carrying them went down while they were reinforcing other troops , officials said . Seven Afghan troops died in that same crash . A U.S. military official said then that insurgents were believed to have shot down the CH-47 Chinook . The Taliban claimed that militants downed the helicopter with a rocket-propelled grenade . More recently , 12 people died last month when a helicopter crashed last month in Afghanistan 's capital city of Kabul . Capt . David Yaryar , an ISAF spokesman , said there was no reported `` insurgent activity in the area '' at the time .
A Black ##hawk plane crashes in Afghanistan , a U.S. military official says . All four of its crew members -- all of them American -- are believed to be dead . People waiting to be picked up saw the aircraft go down , the official says .