Syria’s chemical weapons appear to be secure, U.S. Joint Chiefs of Staff Chairman Gen. Martin Dempsey said.

“On the occasions when we have noted movement, they’ve been movements that appeared to us to be intended to secure them, not to use them,” Dempsey said in a session with reporters on his aircraft returning from Afghanistan. He added that “our ability to have a completely clear understanding is somewhat limited. We don’t have persistent or perfect visibility on” that nation’s chemical weapons intentions.

The Syrian regime headed by Bashar al-Assad has produced, stored and weaponized chemical weapons, yet “little is known from open sources” about the size and condition of the stockpile, the non-partisan Congressional Research Service said in a report in December.

The regime reportedly has stocks of nerve and blister agents such as Sarin, VX and mustard gas and a loss of control over chemical weapons in Syria could have “unpredictable consequences,” the agency said.

The “mosaic of information” obtained to date suggests that the chemical and biological weapons stores are secure, Dempsey said.