The US believes that Russia knew about Syria's chemical attack last week before it happened, even though there is no clear proof, according to a Washington official.
The official claimed that a drone which was operated by the Russians flew over a hospital, whilst the victims of the attack were trying to gain access to treatment.
Only a few hours after the drone left the scene, a Russian-made fighter jet bombed the hospital, according to the Chicago Tribune.
It is not clear whether Syrians or Russians were flying the jet, but US officials believe the bombing was an attempt to cover up the fact that chemical weapons had been used in the attack.
The US believes the drone could not have been a coincidence and therefore Russia surely knew that the chemical attack was going to happen.
However, another official from the US has said Washington has yet to reach a definitive judgement on whether Russia knew about the chemical attack.
Before these officials spoke out, it was said that the US was not sure who was operating the drone.