The cause of the crash on Wednesday of a Ukraine International Airlines Boeing 737-800 outside of Tehran is still in doubt. But Ukrainian officials had suggested that it was possible the aircraft had been shot down by an Iranian-launched air defense missile—and now US intelligence officials have suggested they have evidence that this is the case.

If true, that means that the deaths of the 176 passengers aboard the aircraft were the direct result of the tensions between the United States and Iran.

Video from a witness in Tehran showed the aircraft in flames shortly after takeoff before it crashed in a fireball at a soccer field outside the city. The crew never radioed for help, and telemetry from the 737 was cut off suddenly while it was still in flight.