French intelligence has concluded that forces loyal to Syrian President Bashar Al-Assad carried out a sarin nerve gas attack on April 4 in northern Syria and that Mr. Assad or members of his inner circle ordered the strike, a declassified report showed. The chemical weapons attack on the town of Khan Sheikhoun killed scores of people, according to a war monitor, Syrian opposition groups and Western countries. Mr. Assad has said in two media interviews since April 4 that the evidence of a poison gas attack was false and denied his government had ever used chemical weapons.

The six-page French document — drawn up by France’s military and foreign intelligence services — said it reached its conclusion based on samples they had obtained from the impact strike on the ground and a blood sample from a victim. Among the elements found in the samples were hexamine, a hallmark of sarin produced by the Syrian government, according to the report.

It said the findings matched the results of samples obtained by French intelligence from an attack in Saraqib on April 29, 2013, which Western powers have accused the Assad government of carrying out. “This production process is developed by Syria’s Scientific Studies and Research Center (SSRC) for the regime,” the report said.