A U.S. military helicopter went down in poor weather in Afghanistan on Thursday, a crash that killed all four people on board.

A U.S. defense official who claimed anonymity, says the Black Hawk helicopter crashed in the Regional Command-Southwest area, which includes the traditional Taliban stronghold of Helmand province. Poor weather appeared to have been the cause of the crash.

Almost 3,000 foreign soldiers have died in Afghanistan since the West’s war against the Taliban and other militants began in 2001. Despite a resilient insurgency, the United States, like its NATO allies, plans to withdraw most of its combat troops from the country by the end of 2014.