The international chemical weapons watchdog confirmed Friday that sarin gas was used in the deadly April attack on a Syria town that left more than 80 people dead.

The Organization for the Prohibition of Chemical Weapons said it deployed a team within 24 hours to collect samples, attend autopsies and interview witnesses. Due to security risks, the team was not able to be on the ground in the Khan Shaykhun area where the attack took place, but traveled to a "neighboring country" to conduct its work.

The organization "has confirmed the use of sarin, a nerve agent, at the 4 April incident in Khan Shaykhun in Syria," Director-General Ahmet Uzumcu said in a statement. "I strongly condemn this atrocity, which wholly contradicts the norms enshrined in the Chemical Weapons Convention. The perpetrators of this horrific attack must be held accountable for their crimes."

The watchdog did not identify who was behind the attack, which the U.S. has blamed on Syrian President Bashar Assad. Assad has denied using chemical weapons in Syria's ongoiong civil war.

Horrifying images of suffocating children during the attack drew international condemnation. Days later, President Trump launched a military strike on a Syrian government airbase.

In an unusual move, Trump this week warned the Assad regime that the U.S. was prepared to respond after saying it had detected "potential preparations for another chemical weapons attack." Defense Secretary Jim Mattis said the warning appears to have stopped Assad from carrying out another chemical attack on his own people.

The Organization for the Prohibition of Chemical Weapons report was sent to the U.N. Security Council and was shared with the States Parties to the Chemical Weapons Convention and the watchdog's executive council, which will consider the findings in a July meeting.