The army says the chemical materials found at the factory in the town of Joubar were used by militants before Syrian forces gained control of the area.
The Syrian army also claims that the materials were intended to be used in mortar shells near the capital, Damascus.
Over the past months, Syrian soldiers and Takfiri militants have frequently accused one another of using chemical weapons.
On July 10, Russian Foreign Minister Sergei Lavrov said that the foreign-backed militants in Syria had used chemical weapons.
“Our experts took samples on the spot and studied them in the very lab which is certified by the Organization for the Prohibition of Chemical Weapons and came to the conclusion that both the shell and the sarin it contained were home-made,” the Russian foreign minister said.
Lavrov added that the shells and substances “were made last February in the Syrian territory which at that time was under the control of the Free Syrian Army and made by one of the affiliated armed groups.”
Meanwhile, Washington has rejected the allegations, by saying that chemical attacks in the country are carried out by the Syrian army only.
The Syria crisis began in March 2011, and many people, including large numbers of government forces, have been killed.
Damascus says the chaos is being orchestrated from outside the country, and there are reports that a very large number of the militants are foreign nationals.