The US military has acknowledged that Yemen's Houthi rebels shot down two American MQ-9 Reaper drones in under a week. The first drone was shot down on September 10, and the second on Monday. The General Atomics Reapers, which cost around $30 million each, have been flown by the US military and the CIA over Yemen for years. The Pentagon's press secretary, Maj. Gen. Pat Ryder, says authorities are investigating Monday's downing but declines to provide further details. Ryder also disputes the Houthis' claim that they have shot down 10 Reapers since November.