Story highlights France finds common elements in samples from Khan Sheikhoun and a 2013 Syria attack

French Foreign Ministry says there's "no doubt about the responsibility of the Syrian regime"

(CNN) France has said that it has proof that the Syrian government was behind a chemical weapons attack in Syria earlier 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 developed 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."

French laboratories had stored samples taken from other chemical attacks in Syria and so were able to compare them, he said.

A tweet posted by the French Foreign Ministry said: "There's no doubt that Sarin was used. There is also no doubt about the responsibility of the Syrian regime."