The global chemical weapons watchdog says it has found traces of sarin following an attack in northern Syria in late March, days before a deadly strike using the same nerve agent in another Syrian town.

The Organization for the Prohibition of Chemical Weapons said Thursday that tests found traces of "sarin or sarin-related chemicals" in Ltamenah after a March 30 attack that injured 50 people. No deaths were reported. The organization didn't release further details.

Days later, an April 4 attack in the northwestern town of Khan Sheikhoun killed nearly 100 people. Syria has denied responsibility for that attack. An OPCW-United Nations probe is expected to apportion blame later this month for the Khan Sheikhoun attack.