An account affiliated with Turkey's so-called Operation Olive Branch claimed Kurdish fighters attacked the Free Syrian Army with chlorine gas.
Israel feared a large-scale chemical weapons attack.
The U.S. does have a history of controversial medical experiments elsewhere.
"The thing that scares me the most in the long term is the state of our politics here, and...it's gotten worse," Michael Morell said.
North Korea claims it foiled a joint CIA and South Korean plot on Kim Jong Un's life and blasted Washington's global war on terror.
The Russian leader announced the closure of Russia's last chemical arms facility.
The U.N.'s finding has vindicated the U.S. and its allies.
The two shipments of chemical weapons from North Korea and bound for Syria were intercepted in the last six months.
The head of Russia's Radiation, Chemical and Biological Protection Troops says the new robots will be better equipped than people to operate in deadly environments.
The claims come a week after the Pentagon announced it observed what appear to be preparations for a new chemical attack at a Syrian government airfield.
Syria's President Bashar al-Assad made a series of public appearances, surrounding himself with military officials and supporters amid U.S. threats.
After the U.S. accused Syria of planning another chemical attack against rebels, Russia called such claims "unacceptable."
The White House said Syria is preparing a chemical attack similar to that which prompted a U.S. cruise missile strike in April.
The former president said leaders are often praised for taking military action and criticized for failing to do so. He maintains his decision not to order airstrikes in Syria was the right one.
The Syrian government says it destroyed its stockpiles in 2014.
The April 4 attack on Khan Sheikhoun killed more than 90 people, including 30 children.
The Treasury Department sanctioned 271 scientists of Syria's Scientific Studies and Research Center for their "expertise in chemistry and related disciplines."
North Korea has accused the U.S. of plotting to enact "Plan Jupiter," an alleged biochemical weapons attack meant to topple Kim Jong Un.
Though inspectors tried to remove Syria's chemical arsenal in 2014, evidence of sarin use in a recent strike suggests some remained.
The Islamic State militant group launched two poison gas attacks on Iraqi troops in two days as pro-government forces advanced against the jihadists in their final Iraqi stronghold of Mosul.
The U.S. denied Syrian army reports that a Washington-led coalition struck a cache of toxic substances used by the Islamic State group, killing "hundreds."