US intelligence officials believe Islamic State (ISIS) is using chemical attacks in both Iraq and Syria, an official stated to international media on Thursday night.
"They're using mustard," the individual stated to BBC on condition of anonymity. "We know they are."
"We've seen them use it on at least four separate occasions on both sides of the border – both Iraq and Syria."
Intelligence believes that ISIS has manufactured the mustard gas, not taken stores of the weapon leftover from Syrian President Bashar Assad's regime. Assad was accused of using sarin gas on Syrian citizens in 2013; his chemical stockpile was, allegedly, fully eradicated earlier this year.
"We assess that they have an active chemical weapons little research cell that they're working on to try and get better at it," the official said, adding that the materials and technology are not difficult to obtain to make the gas.
Others maintain that ISIS must have stumbled upon a stockpile during its conquests in Iraq and Syria. In July, several inspectors involved in the Syrian stockpile destruction revealed to the Wall Street Journal that they were deceived – and that Assad had managed to keep significant stores of mustard gas despite the international operation.
Specifically, a red flag was raised for inspectors by Syria's claim of only having 20 tons of mustard agent, given intelligence expectations of hundreds of tons. The regime said it had destroyed hundreds of tons of mustard agent in fire pits before the inspections deal – even though it took other countries decades to destroy similar massive stockpiles.
And in June 2014, ISIS seized a weapons complex thought to have held hundreds of tons of lethal sarin and mustard gasses: the al-Muthanna complex, located 60 miles north of Baghdad, which was a central base of former Iraqi dictator Saddam Hussein's chemical weapons program.
While the US State Department waved off rumors that the plant still held chemical weapons, experts stated to the British Telegraph at the time that the chemical residue left at the site could be weaponized regardless – and that ISIS does, in fact, have chemical weapons experience.
Iraqi soldiers accused ISIS of a chemical gas attack against its soldiers in October 2014, in the most prominent allegation of biochemical weapons use by the group. Two similar attacks were already suspected to have had ISIS involvement at that time.
More recently, US military officials raised the possibility of ISIS having moved to mustard gas attacks in August of this year, stating that early tests point to evidence of at least one such attack on Kurdish Pashmerga forces in July.