Washington, United States
Sep 22, 2016, 05.00 AM (IST)
Initial inspection of the fragments by a small team of US troops proved positive for a mustard agent
A United States defence official on Wednesday said they were probing the possibility that a rocket fired by the Islamic State militants at US forces in Iraq may have carried a chemical agent.
The official said an incoming round had exploded within the base perimeter during an "indirect fire" attack.
He assured that no one was injured in Tuesday's blast near an airfield by the northern town of Qayyarah. No one showed any immediate signs of exposure to the suspected sulfur mustard agent, the official said.
The official downplayed the seriousness of the incident, saying the shell would have been "militarily ineffective."
"Our concern is not much greater after seeing this," he said.
The initial test for a mustard agent proved positive but the second test turned out negative.
A third sample of the suspicious, tar-like black oily substance on the fragments has been sent to a laboratory for analysis.
The troops who handled the fragments went through a standard decontamination procedure.
Lat week, a factory near Mosul suspected of being used by militants to make chemical weapons was run down by US-led coalition warplanes.
Observers have repeatedly alleged IS has used chemical weapons.
Hundreds of US troops are working with Iraqi soldiers to strengthen the airfield ahead of an offensive on the Islamic State stronghold of Mosul.