Drone shot down by Syria vexes Pentagon, White House

Military and intelligence officials continued Friday to comb through clues about what prompted the Syrian military to shoot down an unarmed US Predator drone there earlier this week, US Today reported quoting a senior Defense Department official.
The attack could represent a serious escalation if the Syrians shot the unmanned plane down in a region that had previously been deemed safe for operations. But it appears the mistake may have been on part of US forces who allowed the drone to stray into sensitive airspace, said the senior official and another officer. Both have seen reports about the incident but are not authorized to speak about it publicly.
Reaching a definitive conclusion on the reason for the attack may not come for days, the Pentagon official said.
So far, the Pentagon and White House have declined to say publicly what caused the plane to crash on Tuesday. But White House press secretary Josh Earnest reiterated warnings Thursday that Syrian President Bashar Assad should not to interfere with the air war on extremists from Daesh.
"We certainly continue to believe that that is what the Assad regime should do, which is not interfere with our ongoing efforts there as we deal with [Daesh] and some other extremists that may pose a threat to the United States and our interests around the world," Earnest said. "That — our insistence that they not interfere is — still applies."