0239 GMT December 14, 2019
The Pentagon was "carefully assessing any information that would implicate the Russians knew or assisted with this Syrian capability," a senior military official told reporters at the Pentagon on Friday.
At least 80 people died in Tuesday’s chemical explosion in the town of Khan Shaykhun, which Russia and Syria said was caused by an airstrike on a militant-controlled depot.
The US, however, accused the Syrian government of ordering the attack, a charge Damascus has strongly rejected.
Syria turned over its entire chemical stockpile under a deal negotiated by Russia and the US back in 2013.
Pentagon officials claimed that Syrian forces were possibly assisted by Russia, or at a minimum Russia failed to rein in the Syrian government’s action, the Associated Press reported.
They said Russia had an aviation unit at al-Shayrat airfield, where the US said the chemical attack originated, and had "chemical expertise in the country."
The officials, speaking on condition of anonymity, further said an unmanned aircraft belonging to either Russia or Syria was spotted hovering over the site of the chemical incident after it happened.
The drone reportedly returned to the same area later in the day, just before a hospital - where victims were being treated - was bombed.
"About five hours later, the UAV returned, and the hospital was struck by additional munitions," one official said.
The officials said they suspected the strike on the hospital may have been an effort to destroy evidence of the chemical attack.
President Donald Trump, who said he had a change of mind about Syria after the chemical attack, ordered the US military to take out the airfield by cruise missiles.
Upon the order, the US military launched 59 Tomahawk missiles against several targets on the airbase in Homs province in the early hours of Friday.
The missiles were launched from the USS Porter and USS Ross destroyers in the eastern Mediterranean Sea.
The Syrian government decried the “US aggression,” and said the military attack would only bolster the position of terrorists in the country.
The Kremlin also said Russian President Vladimir Putin regarded the US strike as “an aggression against a sovereign nation” conducted under an “invented pretext.”