The Malaysia Airlines jet that crashed Thursday in Ukraine near the Russian border was shot down by a surface-to-air missile, U.S. officials have confirmed. Intelligence analysts are still trying to determine whether the missile was launched by separatists in Ukraine or Russian forces across the border. Malaysia Airlines lost contact with the aircraft, Flight 17, en route from Amsterdam to Kuala Lumpur with 298 people on board. The Russian news agency Interfax said that the crash was in the Donetsk region of eastern Ukraine, where pro-Russian separatists have been fighting Ukrainian security forces. The U.S. was working to determine whether Americans were on board, said President Barack Obama—who joins other world leaders in a call for an international probe into the jet’s downing.