( CNN) France has said that it has proof that the Syrian government was behind a chemical weapons assault in Syriaearlier this month that killed 89 people.

The French Foreign Minister Jean-Marc Ayrault said that samples taken from the attack on the rebel-held town of Khan Sheikhoun matched those from a previous incident.

“We have definite sources that the procedure used to make the Sarin sampled is typical of the methods are set out in Syrian laboratories, ” he said. “This method bears the signature of the regime, and that is what has allowed us to establish its responsibility in this attack.”

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