The officials say Russia has failed to control the Syrian government's use of chemical weapons.
They say a drone belonging either to Russia or Syria was seen hovering over the site of the chemical weapons attack Tuesday after it happened. The drone returned late in the day as citizens were going to a nearby hospital for treatment. Shortly afterward, officials say the hospital was bombed.
The officials weren't authorized to speak publicly on the matter and demanded anonymity. They say they're still reviewing evidence.
On April 7, U.S. warships launched 59 Tomahawk cruise missiles at a Syrian government airbase following a chemical airstrike in the province of Idlib blamed on President Assad.
UNICEF confirmed at least 27 children had been killed in the attack in Idlib.