Baghdad, Jan 9, SPA -- A U.S. military helicopter which came down in northern Iraq on Sunday killing all 12 aboard had been flying in bad weather, but the cause of the crash was still under investigation, the U.S. military said on Monday. It was one of the deadliest air crashes in Iraq since the start of the U.S.-led invasion of Iraq in 2003. U.S. military spokesman Lieutenant-Colonel Barry Johnson said all 12 aboard the UH-60 Blackhawk helicopter were U.S. citizens. In a separate statement the military said the 12 included eight service personnel and four civilians. "The cause of the crash is still under investigation, but we know the weather was severe at the time," Johnson told Reuters. --SPA 14 35 Local Time 11 35 GMT www.spa.gov.sa/317858