Letters containing a nerve gas ingredient were sent to several locations in Belgium, including the prime minister’s office and the US and British embassies: Belgium Finds Nerve Gas Ingredient in Letters. (Hat tip: zulubaby.)

Two postal workers were taken to hospital after being exposed to the chemicals in the letters at mail depots.

No one else was injured by the 10 letters sent to a variety of targets, also including the Saudi Arabian embassy, three ministries, an airport and a port authority.

The brownish-yellow powder contained phenarsazine chloride, an arsenic derivative used in nerve gas, as well as hydrazine, an agent used as a rocket propellant, the Health Ministry said. Both substances are also found in pesticides.

The letters contained no more than a spoonful of the chemicals — not enough to be life-threatening — but caused irritation to the eyes and skin and affected breathing, Health Ministry spokeswoman Anne-Francoise Gally said.

Police suspect the letters came from a single source in Belgium, said a spokeswoman for the federal prosecutor’s office, overseeing the investigation.

“There are clear indications that the sender of the letters is one and the same person,” Lieve Pellens told VRT television. “There are clear similarities among the letters,” she said, referring to the handwriting on the envelopes.

Pellens said some of them contained a written note reading “International Islamic Society” and “Bastards” in English.