A civil defense member breathes through an oxygen mask, after what rescue workers described as a suspected gas attack in the town of Khan Sheikhoun in rebel-held Idlib.

Initial results of tests on victims of an attack which killed dozens of people in Syria’s Idlib province point to possible exposure to sarin gas, Turkey’s health ministry said on Thursday.

It said 31 people hurt in Tuesday’s attack were being treated in Turkish hospitals and three people had died since being brought from Syria.

“Based on the test results, evidence was detected in patients which leads one to think they were exposed to a chemical substance (sarin),” the statement said.

At least 86 people were killed early on Tuesday in rebel-held Khan Sheikhoun, and dozens more have received treatment for convulsions, breathing problems and foaming at the mouth.

World powers have pointed the finger at the government of Bashar al-Assad, but Foreign Minister Walid Muallem repeated the government’s denial on Thursday.

“The Syrian army has not, did not and will not use this kind of weapons — not just against our own people, but even against the terrorists that attack our civilians with their mortar rounds,” he said.

Russia also stood by its longtime ally, with President Vladimir Putin warning against a rush to judgement.