The Organization for the Prohibition of Chemical Weapons (OPCW) said in a report that there are reasonable grounds to believe that chemical weapons were used in a bomb attack on a Syrian town in 2015.

The commission of inquiry found the use of "corrosive substances," the chemical weapons control agency announced Wednesday.

The experts, however, did not comment on who was responsible for the use of the banned substances.

According to the report, the town of Marea in the north of Aleppo was bombed on Sept. 1, 2015, with both conventional ammunition and projectiles filled with chemicals. A black substance was found at some of the affected sites and a yellow powder at others, according to the OPCW.

People who were exposed to the substances would have developed blisters on their skin a few hours later. A "corrosive substance," which is classified as prohibited in the Chemical Weapons Convention, is said to have been used.

The OPCW was given the task in 2013 to investigate allegations of possible chemical weapons attacks in Syria. The experts interviewed witnesses, examined the evidence, and analyzed soil and biomedical samples.

Previously, they had found that chlorine gas, mustard gas and sarin were used as weapons in other incidents.

Another OPCW commission of inquiry held Syrian regime forces possibly responsible in two cases. Damascus, however, rejected these accusations.

Damascus and its ally Moscow have accused Western powers of using the OPCW for a "politicized" campaign against them.

Syria agreed in 2013 to join the OPCW and give up all chemical weapons, following a suspected sarin attack that killed 1,400 people in the Damascus suburb of Ghouta.

But an OPCW investigation found in April 2020 that the Syrian air force was responsible for sarin and chlorine bombings on the village of Latamneh in 2017.

Damascus then failed to comply with a 90-day deadline by the OPCW's governing body to declare the weapons used in the attacks and reveal its remaining stocks.