Story highlights

NEW: Group: Russian airstrikes in ISIS stronghold kill 42 people, including 27 civilians

NEW: A watchdog official says the new mustard gas report raises "a new level of concern"

A baby may have died after being exposed to the gas in the Syrian town of Marea, the official adds

CNN  — 

The world’s chemical weapons watchdog has determined that mustard gas was used over two months ago in a Syrian town, an official from that group said, raising fresh questions about the deployment of such weaponry in the country’s bloody, messy war.

The August 21 incident in Marea, a town about 28 miles (45 kilometers) north of Aleppo, exposed at least two people “to sulfur mustard, and there is reason to believe that a baby might have also suffered and died as a result,” according to an official with the Organisation for the Prohibition of Chemical Weapons.

The report doesn’t assign blame and even mention any force involved in Syria’s messy, years-long civil war – including ISIS, the terrorist group that’s taken over swaths of the country, or fighters loyal to President Bashar al-Assad.

“It’s very serious because mustard gas is a known chemical weapon,” the OPCW official said. “It’s obviously very, very dangerous and extremely toxic, so it’s a new level of concern.”

Chemical weapons have been a major storyline in Syria’s war, with international forces accusing Assad’s forces of using them against civilians.

Faced with such allegations – not to mention threats of direct force by world powers – Assad’s government agreed in 2013 to give up and turn over its chemical weapons stockpiles. That deal was brokered by the United States and Russia, then signed off on by the United Nations Security Council.

The OPCW – the body in charge of overseeing the process – confirmed in June of last year that the final stockpile had been removed. That’s why fresh claims of such use are such a big deal whether used by the Assad regime or by militant groups, such as ISIS.

Group: Russian strikes killed 42 in ISIS stronghold

Still, the alleged incident in Marea from mustard gas represents a miniscule fraction of the overall bloodshed in the ravaged Middle Eastern nation.

Since the war began more than four years ago, more than 250,000 people have been killed, some 7.6 million have been displaced within Syria and over 4 million have escaped to other countries, U.N. humanitarian affairs chief Stephen O’Brien said late this summer.

In many ways, it has only intensified since O’Brien made those comments – with more players involved, more death and destruction, but still little end in sight or clear victor emerging.

Russia has been among those who have entered the fray recently. Long seen as one of Assad’s staunchest supporters, Moscow has launched airstrikes against what it calls “terrorists” in Syria.

The Syrian Observatory for Human Rights, a London-based monitoring group, reports Russian forces launched particularly deadly airstrikes Tuesday in ISIS’ Syrian stronghold of Raqqa.

Those strikes killed at least 42 people, a figure that includes 27 civilians and 15 ISIS fighters, the group said Friday. It added that ISIS militants “always change their positions in anticipation of shelling.”