A sudden collapse of the government of Syrian President Bashar al-Assad could mean a breakdown in controls over the country’s weapons, U.S. officials and weapons experts said in interviews. But while Libya’s chemical arsenal consists of unwieldy canisters filled mostly with mustard gas, the World War I-era blistering agent, Syria possesses some of the deadliest chemicals ever to be weaponized, dispersed in thousands of artillery shells and warheads that are easy to transport.

Syria’s preferred poison is not mustard gas but sarin, the nerve agent that killed 13 people and sickened about 1,000 during a terrorist attack on the Tokyo subway system in 1995. Sarin, which is lethal if inhaled even in minute quantities, can also be used to contaminate water and food supplies.

Although many analysts doubt that Assad would deliberately share chemical bombs with terrorists, it is not inconceivable that weapons could vanish amid the chaos of an uprising that destroys Syria’s vaunted security services, which safeguard the munitions.