Diplomats say that an investigation by the international chemical weapons watchdog has concluded that sarin or a sarin-like substance was used as a chemical weapon in an April 4 attack on a Syrian town that left more than 90 people dead.

The report by the Organization for the Prohibition of Chemical Weapons into the Khan Sheikhoun attack was not publicly released Thursday, but two diplomats who saw its contents confirmed the key finding that sarin was used.

The report does not apportion blame.

The United States' U.N. envoy, Nikki Haley, said in a statement: "Now that we know the undeniable truth, we look forward to an independent investigation to confirm exactly who was responsible for these brutal attacks so we can find justice for the victims."