Authorities in Iraq’s semiautonomous Kurdish Regional Government (KRG) claim that Islamic State (IS) militants used chlorine gas in an attack against Peshmerga forces.

The KRG’s Security Council released a statement on March 14 that said Peshmerga forces had taken soil and clothing samples after an IS suicide bomber attack in northern Iraq in January.

The statement said the “samples contained levels of chlorine that suggested the substance was used in weaponized form.”

It was not possible to independently verify the claim.

The statement said the analysis was conducted in a European Union certified laboratory after KRG officials handed over the samples collected at the attack site to a “partner nation” in the U.S.-led coalition fighting IS militants in Iraq and Syria.

Peter Sawczak, spokesman for the Dutch-based Organization for the Prohibition of Chemical Weapons (OPCW), said his organization had not received a request from Iraq to investigate the incident so “the OPCW cannot immediately verify the claims.”

The OPCW oversaw the removal of chemical weapons from Syria after reported chemical weapons attacks by Syrian government forces on rebel-held areas.

The January 23 suicide bombing happened between Mosul and the Syrian border where Peshmerga forces were preparing defensive positions after a two-day attack on IS forces, according to the statement.

The statement said Peshmerga forces fired a rocket at an approaching vehicle so there were no casualties except for the bomber but about a dozen Kurdish fighters at the scene experienced nausea, vomiting, dizziness, or weakness.

The U.S. Central Command said on January 30 that an Islamic State chemical weapons expert had been killed in a coalition air strike near Mosul six days earlier.

The expert was identified as Abu Malik, who had been a chemical engineer during Saddam Hussein’s rule and joined Al-Qaeda’s affiliate in Iraq in 2005.

Meanwhile, in northeastern Syria, Kurdish and Christian fighters were reportedly pushing IS militants out of villages in Syria’s Kurdish region.

Nasser Haj Mansour, a defense official in Syria’s Kurdish region, said on March 14 that fighters had captured the Christian village of Tal Maghas in Hassakeh Province that had been under the control of IS militants.

Haj Mansour and the British-based Syrian Observatory for Human Rights both said the village was taken overnight.

Both also said warplanes from the U.S.-led coalition had been pounding IS positions in the area for several days and had continued attacks on March 14 near Tal Tamr village, some 10 kilometers from Tal Maghas.

With reporting by Reuters